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1.
Lactobacillus plantarum is a lactic acid bacterium (LAB) species commonly used as a probiotic. We have sequenced the genome of Lactobacillus plantarum JDM1, which is a Chinese commercial LAB with several probiotic functions, using a GS 20 system. We recommend that each commercial probiotic strain should undergo complete genome sequencing to ensure safety and stability.Lactic acid bacteria (LAB) play a prominent role in the world food supply, performing the main bioconversions in fermented food, and are also used as probiotic supplements in dairy products and other foods. Lactobacillus plantarum is a LAB species commonly used as a probiotic. We have sequenced the genome of Lactobacillus plantarum JDM1, which is a widely used Chinese commercial LAB with several probiotic functions, using a GS 20 system (454 Life Science Corporation) (11). Two hundred thirty-six thousand, five hundred sixty-three high-quality reads were assembled with the 454 assembly tool, which had an average depth of 18.6-fold coverage of the genome and yielded 367 contigs. Among these, 225 large contigs represented 99.17% of the draft sequence. In the finishing process, the order of the selected large contigs was determined by BLAST analysis with the originally published genome sequence of strain WCFS1 (GenBank accession number AL935263) (8). Physical gaps were filled through sequencing of PCR products that spanned these regions using ABI 3730 xl DNA sequencers. Sequence assembly was accomplished by using the Phred/Phrap/Consed software package (4, 7). To ensure final accuracy, the errors in homopolymer sites that arose from the pyrosequencing method were solved via comparison with the corresponding sites on WCFS1 and then resequencing of the ambiguous bases using the ABI 3730 xl DNA sequencer.The complete genome of Lactobacillus plantarum JDM1 contains a single, circular chromosome of 3,197,759 bp and two plasmids (pLP2000 [2,062 bp] and pLP9000 [9,254 bp]). The two plasmids have been sequenced and published, with GenBank accession numbers AY096004 and AY096005 (3). The overall GC content of the chromosome is 44.66%, whereas the plasmids have a GC content slightly lower than that of the chromosome. The entire genome of JDM1 contains 2,948 protein-coding genes, 62 tRNA-encoding genes, and 16 rRNA-encoding genes. Several repeated sequences, designated ISP2, were found in the chromosome which were almost the same as those in WCSF1, identified as a class of transposase-encoding regions representing mobile genetic elements. The other repeated sequence, ISP1 of WCSF1, was absent in JDM1.The entire genomic sequence of L. plantarum JDM1 was a little shorter than that of L. plantarum WCSF1 (3.3 Mb). The two genomes were highly similar (>90% by BLASTN analysis) with respect to genome structure and gene order. Intraspecies diversity may be required for successful adaptation in a complex ecological habitat (2). L. plantarum JDM1 has been grown as a probiotic in rich nutritional medium for so long that the genome may have gradually contracted. As supporting evidence, many sugar transport and metabolism genes in WCFS1 were absent in JDM1.The prophage sequences and locations of JDM1 and WCFS1 are highly variable. L. plantarum JDM1 contains three prophage elements in its genome. R-Pg1, representing a short prophage remnant, is about 14 kb in size, which is similar to R-Lp3 in WCFS1. Pg2 and Pg3 are two ∼39-kb-long prophages that are closely related to Listeria phage B025 (accession no. DQ003639) and the phage Pediococcus pentosaceus ATCC 25745 (accession no. CP000422), respectively.The genomes of LAB evolve actively to adapt to nutritionally rich environments. Even for two strains of the same species, differences obviously exist. The degradation of the genome appears to be an ongoing process not only in all species of Lactobacillus (10) but also in different strains of the same species(2).With the development of better living conditions, the biosafety of food and medicine has received more attention. Lactobacillus bacteria have been supposed to have a “generally accepted as safe” status, but they still have been associated with negative reports (1, 6, 9). More about the functional mechanisms of JDM1 and potential side effects would be explored by complete genome sequencing and data mining. Furthermore, comparative genomics analysis could be carried out with Chinese and European strains. We believe the complete genome of each probiotic strain should be sequenced to ensure safety and stability. At the end of the day, we will get what we pay for in terms of microbial genome sequencing projects (5).  相似文献   

2.
Human milk oligosaccharides (HMOs) are the third-largest solid component of milk. Their structural complexity renders them nondigestible to the host but liable to hydrolytic enzymes of the infant colonic microbiota. Bifidobacteria and, frequently, Bifidobacterium longum strains predominate the colonic microbiota of exclusively breast-fed infants. Among the three recognized subspecies of B. longum, B. longum subsp. infantis achieves high levels of cell growth on HMOs and is associated with early colonization of the infant gut. The B. longum subsp. infantis ATCC 15697 genome features five distinct gene clusters with the predicted capacity to bind, cleave, and import milk oligosaccharides. Comparative genomic hybridizations (CGHs) were used to associate genotypic biomarkers among 15 B. longum strains exhibiting various HMO utilization phenotypes and host associations. Multilocus sequence typing provided taxonomic subspecies designations and grouped the strains between B. longum subsp. infantis and B. longum subsp. longum. CGH analysis determined that HMO utilization gene regions are exclusively conserved across all B. longum subsp. infantis strains capable of growth on HMOs and have diverged in B. longum subsp. longum strains that cannot grow on HMOs. These regions contain fucosidases, sialidases, glycosyl hydrolases, ABC transporters, and family 1 solute binding proteins and are likely needed for efficient metabolism of HMOs. Urea metabolism genes and their activity were exclusively conserved in B. longum subsp. infantis. These results imply that the B. longum has at least two distinct subspecies: B. longum subsp. infantis, specialized to utilize milk carbon, and B. longum subsp. longum, specialized for plant-derived carbon metabolism.The newborn infant not only tolerates but requires colonization by commensal microbes for its own development and health (3). The relevance of the gut microbiome in health and disease is reflected by its influence in a number of important physiological processes, from physical maturation of the developing immune system (28) to the altered energy homeostasis associated with obesity (51, 52).Human milk provides all the nutrients needed to satisfy the neonate energy expenditure and a cadre of molecules with nonnutritional but biologically relevant functions (6). Neonatal health is likely dependent on the timely and complex interactions among bioactive components in human milk, the mucosal immune system, and specialized gut microbial communities (30). Human milk contains complex prebiotic oligosaccharides that stimulated the growth of select bifidobacteria (24, 25) and are believed to modulate mucosal immunity and protect the newborn against pathogens (23, 33, 41). These complex oligosaccharides, which are abundantly present in human milk (their structures are reviewed by Ninonuevo et al. [31] and LoCascio et al. [24]), arrive intact in the infant colon (5) and modulate the composition of neonatal gastrointestinal (GI) microbial communities.Bifidobacteria and, frequently, Bifidobacterium longum strains often predominate the colonic microbiota of exclusively breast-fed infants (10, 11). Among the three subspecies of B. longum, only B. longum subsp. infantis grows robustly on human milk oligosaccharides (HMOs) (24, 25). The availability of the complete genome sequences of B. longum subsp. infantis ATCC 15697 (40) and two other B. longum subsp. longum strains (22, 39) made possible the analysis of whole-genome diversity across the B. longum species. Analysis of the B. longum subsp. infantis ATCC 15697 genome has identified regions predicted to enable the metabolism of HMOs (40); however, their distribution across the B. longum spp. remains unknown. We predict that these regions are exclusively conserved in B. longum strains adapted to colonization of the infant gut microbiome and are therefore capable of robust growth on HMOs. In this work, whole-genome microarray comparisons (comparative genomic hybridizations [CGHs]) were used to associate genotypic biomarkers among 15 B. longum strains exhibiting various HMO utilization phenotypes and host associations.  相似文献   

3.
Zymomonas mobilis is an ethanol-producing alphaproteobacterium currently considered a major candidate organism for bioethanol production. Here we report the finished and annotated genome sequence of Z. mobilis subsp. mobilis strain NCIMB 11163, a British ale-infecting isolate. This is the first Z. mobilis strain whose genome, chromosomal and plasmid, is presented in its entirety.Zymomonas mobilis is a bacterium vigorously studied as a platform organism for bioethanol production in North America and other parts of the world. Z. mobilis converts sugars such as glucose or sucrose into ethanol and carbon dioxide to almost theoretical yields and to rates higher than those of yeasts (17). Genetically engineered strains that ferment pentoses in addition to naturally utilized hexoses also hold great promise for use in lignocellulosic biomass degradations (5, 22). Besides ethanol, Z. mobilis can produce other high-value chemicals such as sorbitol, levan, or phenylacetylcarbinol and has attracted interest for its unusual membrane steroid content (11). Lastly, Zymomonas is regarded as a safe organism and is even used for medicinal purposes (12, 20), which further facilitates its employment in large-scale biotechnological endeavors.The chromosomal sequence of the Z. mobilis subsp. mobilis industrial strain ATCC 31821 (ZM4) was recently published (19). Here we announce the first entire genome sequence of a Z. mobilis subsp. mobilis strain, that of the United Kingdom-originating strain NCIMB 11163 (B70) (20). Total DNA from NCIMB 11163 (16) was used for whole-genome shotgun sequencing at the U.S. DOE Joint Genome Institute. For this, an 8.7-kb DNA library and 454 and Solexa reads were used (http://www.jgi.doe.gov). Draft assemblies were based on 8,551 Sanger reads and 454 pyrosequencing to 20× coverage, whereas the Phred/Phrap/Consed software package was used for sequence assembly and quality assessment (6, 7, 9; http://www.phrap.com). After the shotgun stage, reads were assembled with parallel Phrap (High Performance Software, LLC), and misassemblies were corrected with Dupfinisher (10) or transposon bombing of bridging clones (Epicentre Biotechnologies, Madison, WI). A total of 144 primer walk reactions, five transposon bomb libraries, 53 PCR end reads, and two PCR shatter libraries were necessary to close gaps, resolve repetitive regions, and raise the quality of the finished sequence. The completed genome sequence of NCIMB 11163 was based on 11,048 reads, with an error rate of less than 6 bp out of 100,000 bp.Open reading frame prediction and annotation were performed using Prodigal (http://compbio.ornl.gov/prodigal/) and BLAST (1); tRNAscan-SE and RNAmmer (14, 15) were used for tRNA and rRNA recognition, respectively. Functional assignment of genes was performed by searching translated open reading frames against sequences in the SPTR (TrEMBL) (2), Pfam (8), TIGRFAMs (18), COG (21), and KEGG (13) databases.Z. mobilis NCIMB 11163 contains a single, circular chromosome of 2,124,771 bp and three plasmids, p11163_1, p11163_2, and p11163_3 of 53,380 bp, 40,818 bp, and 4,551 bp, respectively. The overall GC content of the chromosome is 46.83%, whereas those of the plasmids are 42.32%, 43.80%, and 36.37%, respectively. The entire genome of NCIMB 11163 contains 1,884 protein-encoding genes and 51 tRNA and nine rRNA genes, which are chromosomally located.The chromosome of NCIMB 11163 is 68,355 bp larger than that of ZM4 (GenBank accession number NC_006526) (19) and colinear at its largest part with that of ZM4 (genome structure comparisons were performed using ACT) (3). It bears several unique regions, among which are two genomic islands of ca. 25 and 79 kb, with no detectable nucleotide homology to same-species sequences and high regional similarity to chromosomal stretches of Paracoccus denitrificans PD1222 (GenBank accession number CP000489.1), Xanthobacter autotrophicus Py2 (GenBank accession number CP000781.1), and Gluconacetobacter diazotrophicus PAl 5 (GenBank accession number CP001189.1). Genome plasticity in NCIMB 11163 is further indicated by the presence of a type IV secretion system on the 79-kb island, syntenous to the Agrobacterium tumefaciens Ti (IncRh1) conjugal trb system (4), and also by multiple transposase and phage-related genes.In plasmids, housekeeping genes implicated in replication, active partitioning, and plasmid addiction are recognized, as well as genes involved in metabolism, transport, regulation, transposition, and DNA modification. Most notably, p11163_1 bears an arsenical resistance operon inserted in a type II secretion locus, whereas p11163_2, otherwise homologous to the 41-kb ZM4 plasmid (GenBank accession number AY057845), harbors a unique ca. 12-kb CRISPR insertion that interrupts nucleotide colinearity with the aforementioned replicon.  相似文献   

4.
Lactobacillus salivarius is a homofermentative lactic acid bacterium and is frequently isolated from mucosal surfaces of healthy humans. L. salivarius CECT 5713, a strain isolated simultaneously from breast milk and infant feces of a healthy mother-infant pair, has immunomodulatory, anti-inflammatory, and anti-infectious properties, as revealed by several in vitro and in vivo assays. Here, we report its complete and annotated genome sequence.In the last years, culture-dependent and -independent analyses of the bacterial diversity of human milk and colostrum have revealed that these biological fluids are a source of live staphylococci, streptococci, lactic acid bacteria, and bifidobacteria in the infant gut (5, 6, 8, 9, 11, 13), where they play a key role in the initiation and development of the gut microbiota (12). In a previous study, we isolated L. salivarius CECT 5713 from human milk and infant feces of a mother-child pair (10). Subsequent studies revealed that this strain was a good probiotic candidate since it achieved high survival rates when exposed to the gastrointestinal tract conditions, showed a strong adherence to intestinal cells, stimulated the expression of mucin-encoding genes, produced antimicrobial compounds (lactate, acetate, and hydrogen peroxide), and displayed in vivo and in vitro immunomodulatory, anti-inflammatory, and antibacterial properties against pathogenic bacteria (2, 10, 15). Moreover, oral administration of L. salivarius CECT 5713 appears to be an efficient alternative for the treatment of infectious mastitis in lactating women (7). Similarly, studies with other L. salivarius strains in animal models and clinical trials have demonstrated their probiotic function and, particularly, their anti-inflammatory effects (3, 14, 16).In order to interrogate the genome sequence of L. salivarius CECT 5713 with regard to its probiotic properties, the complete genome sequence was determined by a whole-genome shotgun strategy using pyrosequencing technology (454 Life Sciences, Banford, CT). The initial draft assembly provided by 454 Life Sciences was based on 444,604 high-quality pyrosequencing reads, which assembled into 59 contigs. The genome sequence of L. salivarius UCC118 (1), a well-characterized probiotic strain, was used to order these contigs into large scaffolds.The genome of L. salivarius CECT 5713 consists of a circular chromosome of 1,828,169 bp, two plasmids (pHN1, 44,581 bp; pHN2, 20,426 bp), and a megaplasmid (pHN3, 242,962 bp). The overall GC content of the chromosome is 32.93%, similar to that of the megaplasmid but lower than those of the plasmids (>38%). The entire genome of CECT 5713 contains 1,558 protein-, 87 tRNA-, and 51 rRNA-encoding genes. A comparison between the genomes of L. salivarius CECT 5713 and UCC118 revealed the presence of 52 protein-encoding genes that are exclusive for CECT 5713, including genes encoding a 6-phospho-β-glucosidase and three collagen-binding proteins, which may explain the high potential for competitive exclusion of pathogens displayed by this strain. The genes responsible for the bacteriocin activity of L. salivarius CECT 5713 are located in pHN3. This megaplasmid contains six open reading frames (ORFs) closely related, but not identical, to the genes responsible for the biosynthesis of salivaricin ABP-118, a two-component class II bacteriocin (4), in L. salivarius UCC118. Globally, several features of the L. salivarius CECT 5713 genome suggest a strong probiotic potential in humans.  相似文献   

5.
The purpose of this table is to provide the community with a citable record of publications of ongoing genome sequencing projects that have led to a publication in the scientific literature. While our goal is to make the list complete, there is no guarantee that we may have omitted one or more publications appearing in this time frame. Readers and authors who wish to have publications added to this subsequent versions of this list are invited to provide the bibliometric data for such references to the SIGS editorial office.

Non-Bacterial genomes

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6.
Bifidobacteria are normal inhabitants of the human gut. Some strains of this genus are considered health promoting or probiotic, being included in numerous food products. In order to exert their health benefits, these bacteria must overcome biological barriers, including bile salts, to colonize and survive in specific parts of the intestinal tract. The role of multidrug resistance (MDR) transporters in bile resistance of probiotic bacteria and the effect of bile on probiotic gene expression are not fully understood. In the present study, the effect of subinhibitory concentrations of bile on the expression levels of predicted MDR genes from three different bifidobacterial strains, belonging to Bifidobacterium longum subsp. longum, Bifidobacterium breve, and Bifidobacterium animalis subsp. lactis, was tested. In this way, two putative MDR genes whose expression was induced by bile, BL0920 from B. longum and its homolog, Bbr0838, from B. breve, were identified. The expression of the BL0920 gene in Escherichia coli was shown to confer resistance to bile, likely to be mediated by active efflux from the cells. To the best of our knowledge, this represents the first identified bifidobacterial bile efflux pump whose expression is induced by bile.In the gut, commensal bacteria, including those that have health-promoting or probiotic activity, are challenged by the presence of several toxic compounds of intestinal origin, such as bile salts. Bile is secreted into the duodenum to an estimated concentration of 0.2 to 2% for a given bile salt (14). Bile salts are detergent-like compounds with strong antimicrobial activity (2). Therefore, intestinal microorganisms have developed strategies to tolerate physiological concentrations of bile salts during passage through, or colonization of, the gut.Bifidobacteria are common inhabitants of the human gastrointestinal tract (GIT) (19, 39). Some strains of this genus are known to have probiotic activity and are used as functional ingredients in food products around the world (40). The health-promoting effects attributed to these microorganisms are numerous (20, 42). To exert beneficial actions, these bacteria must overcome biological barriers including acid in the stomach and bile in the intestine in order to, at least temporarily, colonize specific parts of the GIT. Thus, understanding the mechanisms of resistance of a given commensal or probiotic microorganism to toxic substances, such as bile salts, is important in the context of its physiology in the GIT. Although bifidobacterial bile tolerance mechanisms are currently poorly understood, bifidobacteria with increased resistance to bile salts have been obtained by progressive adaptation to gradually increasing concentrations of these compounds (27, 29). Through the analysis of such bile-tolerant derivatives, it was shown that the acquisition of bile resistance coincides with changes in membrane protein profiles (27) and carbohydrate metabolism (35, 38), while also conferring cross-resistance to other environmental stresses (29, 36). This indicates that the bifidobacterial response to bile entails a complex cellular activation/repression process, which impacts on general metabolic pathways (37).Specific bile resistance mechanisms have been described in intestinal bacteria, with bile efflux and bile salt hydrolysis being the most prevalent (31). In this respect, multidrug resistance (MDR) transporters seem to play a crucial role in conferring a bile resistance phenotype. MDR proteins are present in all organisms and frequently confer resistance against several structurally unrelated toxic compounds (31). Research on these transporters has mainly been focused on their role in antibiotic resistance. However, given their ubiquitous presence this does not seem to be their primary function. In fact, recent studies support a role for various MDR transporters in allowing microorganisms to survive, establish, and persist in their (human) host (31).It has been shown elsewhere that MDR proteins confer resistance to bile in different enteric bacteria (32). Bile was found to upregulate the expression of the multidrug efflux system cmeABC in Campylobacter jejuni (22), and inhibition of this pump was found to reduce the colonization ability of the microorganism by reducing bile resistance (21). In vitro and in vivo induction of acrAB expression by bile was observed in Vibrio cholerae (6), and also other MDR proteins appear to be induced in this microorganism (5). In the intestinal bacterium Bacteroides fragilis, the expression of different MDR pumps was also found to be upregulated by bile (34).Several MDR systems have been identified in gram-positive bacteria (including probiotic bacteria) (8, 28), but their role in conferring resistance to intestinal toxic compounds, such as bile salts, and the effect of bile on gene expression have not received much scientific attention. Transporters able to extrude bile salts have been found in gram-positive bacteria such as Lactococcus lactis (44, 45) and Lactobacillus johnsonii (7). In Lactobacillus plantarum a membrane protein whose expression is induced by bile, both in vitro and in vivo, was previously identified (3). Proteins conferring resistance to bile, and whose expression is induced by it, have also been reported in other lactobacilli (30, 43). Just a couple of studies have been published on MDR transporters in bifidobacteria. Margolles and coworkers identified and characterized two MDR transporters from Bifidobacterium breve, BbmAB and BbmR, conferring resistance to antimicrobials (25, 26). In Bifidobacterium longum an MDR transporter, Ctr, was found to export cholate from the cell, conferring resistance to this compound when cloned in a heterologous bacterial host (33). However, there is still a knowledge gap with regard to possible effects of bile on MDR gene expression and the potential role of MDR transporters in bile resistance in bifidobacteria.In the present study, the effect of subinhibitory concentrations of bile on the expression levels of genes encoding bifidobacterial MDR protein homologs was tested. For this purpose, known or putative MDR genes were selected from the genomes of different Bifidobacterium strains belonging to the species B. longum, B. breve, and Bifidobacterium animalis. A putative MDR-encoding gene, present as a homolog in both B. breve and B. longum and whose expression was strongly induced by bile, was identified, and the B. longum gene was then characterized.  相似文献   

7.
The purpose of this table is to provide the community with a citable record of publications of ongoing genome sequencing projects that have led to a publication in the scientific literature. While our goal is to make the list complete, there is no guarantee that we may have omitted one or more publications appearing in this time frame. Readers and authors who wish to have publications added to subsequent versions of this list are invited to provide the bibliographic data for such references to the SIGS editorial office.

Phylum Crenarchaeota

Phylum Deinococcus-Thermus

Phylum Proteobacteria

Phylum Tenericutes

Phylum Firmicutes

Phylum Actinobacteria

Phylum Spirochaetes

Non-Bacterial genomes

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8.
Bifidobacteria are important members of the human gut flora, especially in infants. Comparative genomic analysis of two Bifidobacterium animalis subsp. lactis strains revealed evolution by internal deletion of consecutive spacer-repeat units within a novel clustered regularly interspaced short palindromic repeat locus, which represented the largest differential content between the two genomes. Additionally, 47 single nucleotide polymorphisms were identified, consisting primarily of nonsynonymous mutations, indicating positive selection and/or recent divergence. A particular nonsynonymous mutation in a putative glucose transporter was linked to a negative phenotypic effect on the ability of the variant to catabolize glucose, consistent with a modification in the predicted protein transmembrane topology. Comparative genome sequence analysis of three Bifidobacterium species provided a core genome set of 1,117 orthologs complemented by a pan-genome of 2,445 genes. The genome sequences of the intestinal bacterium B. animalis subsp. lactis provide insights into rapid genome evolution and the genetic basis for adaptation to the human gut environment, notably with regard to catabolism of dietary carbohydrates, resistance to bile and acid, and interaction with the intestinal epithelium. The high degree of genome conservation observed between the two strains in terms of size, organization, and sequence is indicative of a genomically monomorphic subspecies and explains the inability to differentiate the strains by standard techniques such as pulsed-field gel electrophoresis.Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes are dominant microbial phyla widely distributed in diverse ecosystems on the planet (10, 13, 20, 23, 33, 40, 51). Metagenomic analyses of the microbial landscape inhabiting various mammalian environments, notably the human gastrointestinal tract (GIT) and skin, have specifically identified Actinobacteria as an important and occasionally dominant phylum (18, 21, 33). Among the members of the large, diverse, and dynamic microbial community residing in the human GIT, Bifidobacterium is a dominant genus considered beneficial to humans and includes probiotic strains (live microorganisms which, when administered in adequate amounts, confer a health benefit on the host) (11). The population of bifidobacteria in the human intestine varies over time. Following vaginal delivery, the GIT of healthy newborns is typically colonized by bifidobacteria, especially in breast-fed infants, during the first few days of life (12). Interindividual variation, however, is remarkable in the human infant intestinal flora (41), and dominant genera are not always consistent across metagenomic analyses of the human gut flora (18, 30, 33, 41). Over time, the infant intestinal ecosystem becomes more complex as the diet becomes more diverse, with bifidobacteria typically remaining dominant until weaning (30).Bifidobacterium animalis subsp. lactis is a gram-positive lactic acid bacterium commonly found in the guts of healthy humans and has been identified in the infant gut biota, particularly in ileal, fecal, and mucosal samples (52, 56). Some strains of B. animalis subsp. lactis are able to survive in the GIT, to adhere to human epithelial cells in vitro, to modify fecal flora, to modulate the host immune response, or to prevent microbial gastroenteritis and colitis (4, 15, 20, 40, 52, 56). Additionally, B. animalis subsp. lactis has been reported to utilize nondigestible oligosaccharides, which may contribute to the organism''s ability to compete in the human gut. Carbohydrates resistant to enzymatic degradation and not absorbed in the upper intestinal tract are a primary source of energy for microbes residing in the large intestine. The benefits associated with probiotic strains of B. animalis subsp. lactis have resulted in their inclusion in the human diet via formulation into a large array of dietary supplements and foods, including dairy products such as yogurt. Deciphering the complete genome sequences of such microbes will provide additional insight into the genetic basis for survival and residence in the human gut, notably with regard to the ability to survive gastric passage and utilize available nutrients. Also, these genomes provide reference sequences for ongoing metagenomic analyses of the human environment, including the gut metagenome.Bifidobacterium animalis subsp. lactis is the most common bifidobacterium utilized as a probiotic in commercial dairy products in North America and Europe (22, 38). However, despite this commercial and probiotic significance, strain-level differentiation of B. animalis subsp. lactis strains has been hindered by the high genetic similarity of these organisms, as determined by pulsed-field gel electrophoresis and other nucleic acid-based techniques (6, 55, 56), and the lack of available genomic sequence information. The genome sequence of strain BB-12 (17) is not currently publicly available, and only a draft genome sequence in 28 contigs is available for strain HN019 (GenBank project 28807). The complete B. animalis subsp. lactis genome for strain AD011 (28) was only recently (2009) published. While this was an important first step, a single genome does not allow identification of unique targets for strain differentiation or comparative analyses within the subspecies.The objectives of this study were to determine the complete genome sequences of two B. animalis subsp. lactis strains, the type strain and a widely used commercial strain, to provide insights into the functionality of this species and into species identification and strain specialization.  相似文献   

9.
Bocavirus is a newly classified genus of the family Parvovirinae. Infection with Bocavirus minute virus of canines (MVC) produces a strong cytopathic effect in permissive Walter Reed/3873D (WRD) canine cells. We have systematically characterized the MVC infection-produced cytopathic effect in WRD cells, namely, the cell death and cell cycle arrest, and carefully examined how MVC infection induces the cytopathic effect. We found that MVC infection induces an apoptotic cell death characterized by Bax translocalization to the mitochondrial outer membrane, disruption of the mitochondrial outer membrane potential, and caspase activation. Moreover, we observed that the activation of caspases occurred only when the MVC genome was replicating, suggesting that replication of the MVC genome induces apoptosis. MVC infection also induced a gradual cell cycle arrest from the S phase in early infection to the G2/M phase at a later stage, which was confirmed by the upregulation of cyclin B1 and phosphorylation of cdc2. Cell cycle arrest at the G2/M phase was reproduced by transfection of a nonreplicative NS1 knockout mutant of the MVC infectious clone, as well as by inoculation of UV-irradiated MVC. In contrast with other parvoviruses, only expression of the MVC proteins by transfection did not induce apoptosis or cell cycle arrest. Taken together, our results demonstrate that MVC infection induces a mitochondrion-mediated apoptosis that is dependent on the replication of the viral genome, and the MVC genome per se is able to arrest the cell cycle at the G2/M phase. Our results may shed light on the molecular pathogenesis of Bocavirus infection in general.The Bocavirus genus is newly classified within the subfamily Parvovirinae of the family Parvoviridae (21). The currently known members of the Bocavirus genus include bovine parvovirus type 1 (BPV1) (17), minute virus of canines (MVC) (57), and the recently identified human bocaviruses (HBoV, HBoV2, and HBoV3) (4, 7, 36).MVC was first recovered from canine fecal samples in 1970 (10). The virus causes respiratory disease with breathing difficulty (14, 32, 49) and enteritis with severe diarrhea (11, 39), which often occurs with coinfection with other viruses (39), spontaneous abortion of fetuses, and death of newborn puppies (14, 29). Pathological lesions in fetuses in experimental infections were found in the lymphoid tissue of the lung and small intestine (14). MVC was isolated and grown in the Walter Reed/3873D (WRD) canine cell line (10), which is derived from a subdermoid cyst of an irradiated male dog (10). The full-length 5.4-kb genome of MVC was recently mapped with palindromic termini (60). Under the control of a single P6 promoter, through the mechanism of alternative splicing and alternative polyadenylation, MVC expresses two nonstructural proteins (NS1 and NP1) and two capsid proteins (VP1 and VP2). Like the NS1 proteins of other parvoviruses, the NS1 of MVC is indispensable for genome replication. The NP1 protein, which is unique to the Bocavirus genus, appears to be critical for optimal viral replication, as the NP1 knockout mutant of MVC suffers from severe impairment of replication (60). A severe cytopathic effect during MVC infection of WRD cells has been documented (10, 60).The HBoV genome has been frequently detected worldwide in respiratory specimens from children under 2 years old with acute respiratory illnesses (2, 34, 55). HBoV is associated with acute expiratory wheezing and pneumonia (3, 34, 55) and is commonly detected in association with other respiratory viruses (34, 55). Further studies are necessary, however, to identify potential associations of HBoV infection with clinical symptoms or disease of acute gastroenteritis (7, 36). The full-length sequence of infectious MVC DNA (GenBank accession no. FJ214110) that we have reported shows 52.6% identity to HBoV, while the NS1, NP1, and VP1 proteins are 38.5%, 39.9%, and 43.7% identical to those of HBoV, respectively (60).The cytopathic effect induced during parvovirus infection has been widely documented, e.g., in infections with minute virus of mice (MVM) (13), human parvovirus B19 (B19V) (58), parvovirus H-1 (25, 52), and BPV1 (1). In Bocavirus, cell death during BPV1 infection of embryonic bovine tracheal cells has been shown to be achieved through necrosis, independent of apoptosis (1). B19V-induced cell death of primary erythroid progenitor cells has been shown to be mainly mediated by an apoptotic pathway (58) in which the nonstructural protein 11kDa plays a key role (16). In contrast, the MVM-induced cytopathic effect has been revealed to be mediated by NS1 interference with intracellular casein kinase II (CKII) signaling (22, 44, 45), a nonapoptotic cell death. Oncolytic parvovirus H-1 infections can induce either apoptosis or nonapoptotic cell death, depending on the cell type (25, 40). Therefore, the mechanisms underlying parvovirus infection-induced cell death vary, although NS1 has been widely shown to be involved in both apoptotic and nonapoptotic cell death. The nature of the cytopathic effect during Bocavirus MVC infection has not been studied.Parvovirus replication requires infected cells at the S phase. Infection with parvovirus has been revealed to accompany a cell cycle perturbation that mostly leads to an arrest in the S/G2 phase or the G2/M phase during infection (30, 33, 42, 47, 65). MVM NS1 expression induces an accumulation of sensitive cells in the S/G2 phase (6, 46, 47). Whether MVC infection-induced cell death is accompanied by an alternation of cell cycle progression and whether the viral nonstructural protein is involved in these processes have not been addressed.In this study, we found, in contrast with other members of the family Parvoviridae, expression of both the nonstructural and structural proteins of MVC by transfection did not induce cell death or cell cycle arrest. However, the cytopathic effect induced during MVC infection is a replication-coupled, mitochondrion-mediated and caspase-dependent apoptosis, accompanied with a gradual cell cycle arrest from the S phase to the G2/M phase, which is facilitated by the MVC genome.  相似文献   

10.
A multilocus sequence typing (MLST) analysis was used to examine the genetic structure and diversity within the two large extrachromosomal replicons in Medicago-nodulating rhizobia (Sinorhizobium meliloti and Sinorhizobium medicae). The allelic diversity within these replicons was high compared to the reported diversity within the corresponding chromosomes of the same strains (P. van Berkum et al., J. Bacteriol. 188:5570-5577, 2006). Also, there was strong localized linkage disequilibrium (LD) between certain pSymA loci: e.g., nodC and nifD. Although both of these observations could be explained by positive (or diversifying) selection by plant hosts, results of tests for positive selection did not provide consistent support for this hypothesis. The strong LD observed between the nodC and nifD genes could also be explained by their close proximity on the pSymA replicon. Evidence was obtained that some nodC alleles had a history of intragenic recombination, while other alleles of this locus had a history of intergenic recombination. Both types of recombination were associated with a decline in symbiotic competence with Medicago sativa as the host plant. The combined observations of LD between the nodC and nifD genes and intragenic recombination within one of these loci indicate that the symbiotic gene region on the pSymA plasmid has evolved as a clonal segment, which has been laterally transferred within the natural populations.Plants of the genus Medicago are legumes that often benefit from a mutualistic symbiosis with rhizobia. The most agriculturally significant species of rhizobia that nodulate these plants are Sinorhizobium meliloti (9) and Sinorhizobium medicae (22). Previously reported population genetic analyses of these bacteria have focused on the study of how allelic variants at multiple loci are distributed within and among natural populations (2, 3, 10, 26, 31, 32). This was also the focus of the present study, but it was extended by examining more loci in many more strains of both species of Sinorhizobium coupled with an analysis having a range of symbiotic genotypes. One goal was to determine if there were any obvious correlations between the megaplasmid genotypes observed and their symbiotic competence. A second goal was to determine if selection by their host plants may have influenced the evolution of their symbiotic relationships.The genes for symbiosis reside on the extrachromosomal replicons pSymA (1,354,226 nucleotides [nt]) and pSMED02 (1,245,408 nt) in the genomes of S. meliloti Rm1021 and S. medicae WSM419, respectively (GenBank accession no. AE006469 and CP000740, respectively). Besides these two plasmids, these two strains each harbor one other large extrachromosomal replicon, pSymB (1,683,333 nt) and pSMED01 (1,570,951 nt), respectively (GenBank accession no. AL591985 and CP000739, respectively).Multilocus sequence typing (MLST) (16) is a form of genomic indexing that is commonly used to study the population genetic structure and phylogenetic relatedness within diverse groups of bacteria. In this method, nucleotide sequences of a fixed set of common loci are obtained from a collection of strains, and polymorphic sites among these sequences are used to derive an allelic profile or sequence type (ST) for each genome. Comparisons of the resulting data can be used to infer phylogenetic relationships among the organisms in the sample population, and they also can be used to infer how evolutionary processes, such as recombination and selection, have shaped the genetic structure of the population. For example, levels of intergenic recombination among chromosomal genes in natural populations of Neisseria meningitidis reportedly are relatively high, while corresponding levels within populations of Staphylococcus aureus were low (28). Depending on the specific pairs of loci examined, the levels of linkage disequilibrium (LD) (a lack of intergenic recombination) among several chromosomally carried core genes of S. meliloti were reported to be generally moderate to high (26).The MLST approach has been used to confirm that the chromosomes of S. meliloti and S. medicae are sexually isolated (2, 3, 31) and to provide evidence that horizontal gene transfer (HGT) does occur between the symbiotic megaplasmids of these species (3, 32). It has also been used to demonstrate that levels of intergenic recombination, as indicated by linkage disequilibrium, differ between the three replicons of S. meliloti (26). Levels of intergenic recombination within the pSymB replicons of these strains are generally high, unlike the chromosomes and pSymA replicons within the same strains (26). Bailly et al. (3) hypothesized that the region of the pSymA plasmid that contains the nodulation (nod) genes is frequently transferred in natural populations. They also suggested that selective pressures from the host plant may have influenced both nod gene diversity and patterns of polymorphism across the entire nod gene region.In the present study, multilocus allelic variation of the two megaplasmids was examined among 231 Medicago-nodulating rhizobia that originated primarily from southwest Asia (10). Previously, 91 different chromosomal sequence types (STs) were identified among the same strains from sequence variation in 10 loci (31). This collection of strains had earlier been divided into two closely related groups based on results of multilocus enzyme electrophoresis (10), and this result was subsequently cited in support of separating the Medicago-nodulating rhizobia into the two species S. meliloti and S. medicae (22).The objectives of this study were (i) to use MLST to examine the genetic relationships within and among the large extrachromosomal replicons in S. meliloti and S. medicae, (ii) to estimate levels of intergenic and intragenic recombination in these replicons, (iii) to evaluate the nitrogen-fixing competence of representative symbiotic genotypes with Medicago sativa, and (iv) to determine whether positive (or diversifying) selection may have influenced the genetic structure of the megaplasmids.  相似文献   

11.
For Bovine viral diarrhea virus (BVDV), the type species of the genus Pestivirus in the family Flaviviridae, cytopathogenic (cp) and noncytopathogenic (ncp) viruses are distinguished according to their effect on cultured cells. It has been established that cytopathogenicity of BVDV correlates with efficient production of viral nonstructural protein NS3 and with enhanced viral RNA synthesis. Here, we describe generation and characterization of a temperature-sensitive (ts) mutant of cp BVDV strain CP7, termed TS2.7. Infection of bovine cells with TS2.7 and the parent CP7 at 33°C resulted in efficient viral replication and a cytopathic effect. In contrast, the ability of TS2.7 to cause cytopathogenicity at 39.5°C was drastically reduced despite production of high titers of infectious virus. Further experiments, including nucleotide sequencing of the TS2.7 genome and reverse genetics, showed that a Y1338H substitution at residue 193 of NS2 resulted in the temperature-dependent attenuation of cytopathogenicity despite high levels of infectious virus production. Interestingly, TS2.7 and the reconstructed mutant CP7-Y1338H produced NS3 in addition to NS2-3 throughout infection. Compared to the parent CP7, NS2-3 processing was slightly decreased at both temperatures. Quantification of viral RNAs that were accumulated at 10 h postinfection demonstrated that attenuation of the cytopathogenicity of the ts mutants at 39.5°C correlated with reduced amounts of viral RNA, while the efficiency of viral RNA synthesis at 33°C was not affected. Taken together, the results of this study show that a mutation in BVDV NS2 attenuates viral RNA replication and suppresses viral cytopathogenicity at high temperature without altering NS3 expression and infectious virus production in a temperature-dependent manner.The pestiviruses Bovine viral diarrhea virus-1 (BVDV-1), BVDV-2, Classical swine fever virus (CSFV), and Border disease virus (BDV) are causative agents of economically important livestock diseases. Together with the genera Flavivirus, including several important human pathogens like Dengue fever virus, West Nile virus, Yellow fever virus, and Tick-borne encephalitis virus, and Hepacivirus (human Hepatitis C virus [HCV]), the genus Pestivirus constitutes the family Flaviviridae (8, 20). All members of this family are enveloped viruses with a single-stranded positive-sense RNA genome encompassing one large open reading frame (ORF) flanked by 5′ and 3′ nontranslated regions (NTR) (see references 8 and 28 for reviews). The ORF encodes a polyprotein which is co- and posttranslationally processed into the mature viral proteins by viral and cellular proteases. For BVDV, the RNA genome is about 12.3 kb in length and encodes a polyprotein of about 3,900 amino acids. The first third of the ORF encodes a nonstructural (NS) autoprotease and four structural proteins, while the remaining part of the genome encodes NS proteins which share many common characteristics and functions with the corresponding NS proteins encoded by the HCV genome (8, 28). NS2 of BVDV represents a cysteine autoprotease which is distantly related to the HCV NS2-3 protease (26). NS3, NS4A, NS4B, NS5A, and NS5B are essential components of the pestivirus replicase (7, 10, 49). NS3 possesses multiple enzymatic activities, namely serine protease (48, 52, 53), NTPase (46), and helicase activity (51). NS4A acts as an essential cofactor for the NS3 proteinase. NS5B represents the RNA-dependent RNA polymerase (RdRp) (22, 56). The functions of NS4B and NS5A remain to be determined. NS5A has been shown to be a phosphorylated protein that is associated with cellular serine/threonine kinases (44).According to their effects in tissue culture, two biotypes of pestiviruses are distinguished: cytopathogenic (cp) and noncytopathogenic (ncp) viruses (17, 27). The occurrence of cp BVDV in cattle persistently infected with ncp BVDV is directly linked to the induction of lethal mucosal disease in cattle (12, 13). Previous studies have shown that cp BVDV strains evolved from ncp BVDV strains by different kinds of mutations. These include RNA recombination with various cellular mRNAs, resulting in insertions of cellular protein-coding sequences into the viral genome, as well as insertions, duplications, and deletions of viral sequences, and point mutations (1, 2, 9, 24, 33, 36, 37, 42). A common consequence of all these genetic changes in cp BVDV genomes is the efficient production of NS3 at early and late phases of infection. In contrast, NS3 cannot be detected in cells at late time points after infection with ncp BVDV. An additional major difference is that the cp viruses produce amounts of viral RNA significantly larger than those of their ncp counterparts (7, 32, 50). While there is clear evidence that cell death induced by cp BVDV is mediated by apoptosis, the molecular mechanisms involved in pestiviral cytopathogenicity are poorly understood. In particular, the role of NS3 in triggering apoptosis remains unclear. It has been hypothesized that the NS3 serine proteinase might be involved in activation of the apoptotic proteolytic cascade (21, 55). Furthermore, it has been suggested that the NS3-mediated, enhanced viral RNA synthesis of cp BVDV and subsequently larger amounts of viral double-stranded RNAs may play a crucial role in triggering apoptosis (31, 54).In this study, we describe generation and characterization of a temperature-sensitive (ts) cp BVDV mutant whose ability to cause viral cytopathogenicity at high temperature is strongly attenuated. Our results demonstrate that a single amino acid substitution in NS2 attenuates BVDV cytopathogenicity at high temperature without affecting production of infectious viruses and expression of NS3 in a temperature-dependent manner.  相似文献   

12.
The purpose of this table is to provide the community with a citable record of publications of ongoing genome sequencing projects that have led to a publication in the scientific literature. While our goal is to make the list complete, there is no guarantee that we may have omitted one or more publications appearing in this time frame. Readers and authors who wish to have publications added to subsequent versions of this list are invited to provide the bibliographic data for such references to the SIGS editorial office.

Non-Bacterial genomes

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13.
Analysis of Lyme borreliosis (LB) spirochetes, using a novel multilocus sequence analysis scheme, revealed that OspA serotype 4 strains (a rodent-associated ecotype) of Borrelia garinii were sufficiently genetically distinct from bird-associated B. garinii strains to deserve species status. We suggest that OspA serotype 4 strains be raised to species status and named Borrelia bavariensis sp. nov. The rooted phylogenetic trees provide novel insights into the evolutionary history of LB spirochetes.Multilocus sequence typing (MLST) and multilocus sequence analysis (MLSA) have been shown to be powerful and pragmatic molecular methods for typing large numbers of microbial strains for population genetics studies, delineation of species, and assignment of strains to defined bacterial species (4, 13, 27, 40, 44). To date, MLST/MLSA schemes have been applied only to a few vector-borne microbial populations (1, 6, 30, 37, 40, 41, 47).Lyme borreliosis (LB) spirochetes comprise a diverse group of zoonotic bacteria which are transmitted among vertebrate hosts by ixodid (hard) ticks. The most common agents of human LB are Borrelia burgdorferi (sensu stricto), Borrelia afzelii, Borrelia garinii, Borrelia lusitaniae, and Borrelia spielmanii (7, 8, 12, 35). To date, 15 species have been named within the group of LB spirochetes (6, 31, 32, 37, 38, 41). While several of these LB species have been delineated using whole DNA-DNA hybridization (3, 20, 33), most ecological or epidemiological studies have been using single loci (5, 9-11, 29, 34, 36, 38, 42, 51, 53). Although some of these loci have been convenient for species assignment of strains or to address particular epidemiological questions, they may be unsuitable to resolve evolutionary relationships among LB species, because it is not possible to define any outgroup. For example, both the 5S-23S intergenic spacer (5S-23S IGS) and the gene encoding the outer surface protein A (ospA) are present only in LB spirochete genomes (36, 43). The advantage of using appropriate housekeeping genes of LB group spirochetes is that phylogenetic trees can be rooted with sequences of relapsing fever spirochetes. This renders the data amenable to detailed evolutionary studies of LB spirochetes.LB group spirochetes differ remarkably in their patterns and levels of host association, which are likely to affect their population structures (22, 24, 46, 48). Of the three main Eurasian Borrelia species, B. afzelii is adapted to rodents, whereas B. valaisiana and most strains of B. garinii are maintained by birds (12, 15, 16, 23, 26, 45). However, B. garinii OspA serotype 4 strains in Europe have been shown to be transmitted by rodents (17, 18) and, therefore, constitute a distinct ecotype within B. garinii. These strains have also been associated with high pathogenicity in humans, and their finer-scale geographical distribution seems highly focal (10, 34, 52, 53).In this study, we analyzed the intra- and interspecific phylogenetic relationships of B. burgdorferi, B. afzelii, B. garinii, B. valaisiana, B. lusitaniae, B. bissettii, and B. spielmanii by means of a novel MLSA scheme based on chromosomal housekeeping genes (30, 48).  相似文献   

14.
Water channels formed by aquaporins (AQPs) play an important role in the control of water homeostasis in individual cells and in multicellular organisms. Plasma membrane intrinsic proteins (PIPs) constitute a subclass of plant AQPs. TgPIP2;1 and TgPIP2;2 from tulip petals are members of the PIP family. In this study, we overexpressed TgPIP2;1 and TgPIP2;2 in Pichia pastoris and monitored their water channel activity (WCA) either by an in vivo spheroplast-bursting assay performed after hypo-osmotic shock or by growth assay. Osmolarity, pH, and inhibitors of AQPs, protein kinases (PKs), and protein phosphatases (PPs) affect the WCA of heterologous AQPs in this expression system. The WCA of TgPIP2;2-expressing spheroplasts was affected by inhibitors of PKs and PPs, which indicates that the water channel of this homologue is regulated by phosphorylation in P. pastoris. From the results reported herein, we suggest that P. pastoris can be employed as a heterologous expression system to assay the WCA of PIPs and to monitor the AQP-mediated channel gating mechanism, and it can be developed to screen inhibitors/effectors of PIPs.The movement of water across cell membranes has long been thought to occur by free diffusion through the lipid bilayer. However, the discovery of the membrane protein CHIP28 in red blood cells has suggested the involvement of protein channels (29), and it is now well established that transmembrane water permeability is facilitated by aquaporins (AQPs), water channel proteins that are found in bacteria, fungi, plants, and animals (1, 7, 13, 24). AQPs contain six transmembrane α-helices and five connecting loops, and both the N and C termini are located in the cytosol. The monomers assemble into tetrameric complexes, with each monomer forming an individual water channel (11, 14, 24, 33). Apart from the exceptions of AQP11 and AQP12 from mice, as described by K. Ishibashi (15), AQPs have two signature Asn-Pro-Ala motifs, which are located in the second intracellular and the fifth extracellular loops, B and E.While 13 different AQPs have been identified in mammals (16), more than 33 AQP homologues have been discovered in plants (6, 17, 30). Plant AQPs fall into four subclasses: (i) the plasma membrane (PM) intrinsic proteins (PIPs), which are localized in the PM; (ii) the tonoplast intrinsic proteins (TIPs), which are localized in the vacuolar membranes; (iii) the nodulin-26-like intrinsic proteins; and (iv) the small basic intrinsic proteins (24). In Arabidopsis and maize, there are 13 PIPs, which can be divided further into two subfamilies, PIP1 and PIP2 (6, 17).The functions and mechanisms of regulation of plant AQPs have been extensively investigated (7, 13, 18, 24). There have been several reports on the water channel activity (WCA) of specific AQPs and their regulation by protein phosphorylation (3, 4, 8, 12, 18, 25, 32, 33). It has been shown that the WCA of the PIP2 member SoPIP2;1 from spinach is regulated by phosphorylation at two Ser residues (19, 33).The physiologically interesting temperature-dependent opening and closing of tulip (Tulipa gesneriana) petals occur concomitantly with water transport and are regulated by reversible phosphorylation of an undefined PIP (4, 5). Recently, four PIP homologues were isolated from tulip petals, and their WCAs have been analyzed by heterologous expression in Xenopus laevis oocytes (3). It has been shown that the tulip PIP TgPIP2;2 (DDBJ/EMBL/GenBank accession no. AB305617) is ubiquitously expressed in all organs of the tulip and that TgPIP2;2 is the most likely of the TgPIP homologues to be modulated by the reversible phosphorylation that regulates transcellular water transport and mediates petal opening and closing (3, 4). However, while the members of the PIP2 subfamily are characterized as water channels (6), TgPIP2;1 (DDBJ/EMBL/GenBank accession no. AB305616) shows no significant WCA in the oocyte expression system (3). There is growing interest in research on AQPs due to their crucial roles in the physiology of plants and animals (1, 16, 21-24, 26-28, 36). The assay of AQP channel activity is usually performed using either a X. laevis oocyte expression system (29) or a stopped-flow light-scattering spectrophotometer (35), both of which are not widely available. Furthermore, the complexity of these methods and requirement of expertise limit their high-throughput applications. In contrast, a Pichia pastoris expression system is simple to use, inexpensive, and feasible and can be used in high-throughput applications. Although a P. pastoris expression system has been shown to assay the WCA of a TIP (9), extensive research is necessary with other AQPs such as PIPs or AQPs present in intragranular membranes to establish whether this assay system can be used to characterize a water channel and study its regulation mechanisms. With this in view, in the study reported herein, TgPIP2;1 and TgPIP2;2 have been heterologously expressed in P. pastoris, and their WCAs have been assayed. The effects of several factors, such as osmolarity, pH, and inhibitors of protein kinases (PKs) and protein phosphatases (PPs), on the WCA of the recombinant P. pastoris have been investigated. Based on the results, we demonstrate that the P. pastoris heterologous expression system can be used to rapidly characterize PIP channels, to monitor the effects of mutations, and to score the effects of inhibitors and abiotic factors.  相似文献   

15.
The purpose of the present study was to investigate the inhibition of Vibrio by Roseobacter in a combined liquid-surface system. Exposure of Vibrio anguillarum to surface-attached roseobacters (107 CFU/cm2) resulted in significant reduction or complete killing of the pathogen inoculated at 102 to 104 CFU/ml. The effect was likely associated with the production of tropodithietic acid (TDA), as a TDA-negative mutant did not affect survival or growth of V. anguillarum.Antagonistic interactions among marine bacteria are well documented, and secretion of antagonistic compounds is common among bacteria that colonize particles or surfaces (8, 13, 16, 21, 31). These marine bacteria may be interesting as sources for new antimicrobial drugs or as probiotic bacteria for aquaculture.Aquaculture is a rapidly growing sector, but outbreaks of bacterial diseases are a limiting factor and pose a threat, especially to young fish and invertebrates that cannot be vaccinated. Because regular or prophylactic administration of antibiotics must be avoided, probiotic bacteria are considered an alternative (9, 18, 34, 38, 39, 40). Several microorganisms have been able to reduce bacterial diseases in challenge trials with fish or fish larvae (14, 24, 25, 27, 33, 37, 39, 40). One example is Phaeobacter strain 27-4 (17), which inhibits Vibrio anguillarum and reduces mortality in turbot larvae (27). The antagonism of Phaeobacter 27-4 and the closely related Phaeobacter inhibens is due mainly to the sulfur-containing tropolone derivative tropodithietic acid (TDA) (2, 5), which is also produced by other Phaeobacter strains and Ruegeria mobilis (28). Phaeobacter and Ruegeria strains or their DNA has been commonly found in marine larva-rearing sites (6, 17, 28).Phaeobacter and Ruegeria (Alphaproteobacteria, Roseobacter clade) are efficient surface colonizers (7, 11, 31, 36). They are abundant in coastal and eutrophic zones and are often associated with algae (3, 7, 41). Surface-attached Phaeobacter bacteria may play an important role in determining the species composition of an emerging biofilm, as even low densities of attached Phaeobacter strain SK2.10 bacteria can prevent other marine organisms from colonizing solid surfaces (30, 32).In continuation of the previous research on roseobacters as aquaculture probiotics, the purpose of this study was to determine the antagonistic potential of Phaeobacter and Ruegeria against Vibrio anguillarum in liquid systems that mimic a larva-rearing environment. Since production of TDA in liquid marine broth appears to be highest when roseobacters form an air-liquid biofilm (5), we addressed whether they could be applied as biofilms on solid surfaces.  相似文献   

16.
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17.
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18.
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19.
The purpose of this table is to provide the community with a citable record of publications of ongoing genome sequencing projects that have led to a publication in the scientific literature. While our goal is to make the list complete, there is no guarantee that we may have omitted one or more publications appearing in this time frame. Readers and authors who wish to have publications added to subsequent versions of this list are invited to provide the bibliographic data for such references to the SIGS editorial office.

Phylum Euryarchaeota

Phylum Crenarchaeota

Phylum Deinococcus-Thermus

Phylum Proteobacteria

Phylum Tenericutes

Phylum Firmicutes

Phylum Actinobacteria

Non-Bacterial genomes

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20.
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