Improved Degradation of Monochlorophenols by a Constructed Strain

Pseudomonas sp. strain B13, a strain able to degrade 3-chlorobenzoate and, after prolonged adaptation (40 days), 4-chlorophenol, could transfer the ability to degrade chlorocatechols to a recipient, Alcaligenes sp. strain A7, which is able to grow with benzoate and phenol. Representative transconjugants, such as Alcaligenes sp. strain A7-2, were able to utilize all three isomeric chlorophenols; this property was not possessed by the donor or the recipient. The ability to grow readily with 4-chlorophenol may be attributable to a more rapid induction of phenol hydroxylase by Alcaligenes sp. strain A7-2 than by Pseudomonas sp. strain B13, a property which correlates with the greater level of resistance to chlorophenols shown by the transconjugant.     

Genomic Responses to Arsenic in the Cyanobacterium Synechocystis sp. PCC 6803

Arsenic is a ubiquitous contaminant and a toxic metalloid which presents two main redox states in nature: arsenite [As^III] and arsenate [As^V]. Arsenic resistance in Synechocystis sp. strain PCC 6803 is mediated by the arsBHC operon and two additional arsenate reductases encoded by the arsI1 and arsI2 genes. Here we describe the genome-wide responses to the presence of arsenate and arsenite in wild type and mutants in the arsenic resistance system. Both forms of arsenic produced similar responses in the wild type strain, including induction of several stress related genes and repression of energy generation processes. These responses were transient in the wild type strain but maintained in time in an arsB mutant strain, which lacks the arsenite transporter. In contrast, the responses observed in a strain lacking all arsenate reductases were somewhat different and included lower induction of genes involved in metal homeostasis and Fe-S cluster biogenesis, suggesting that these two processes are targeted by arsenite in the wild type strain. Finally, analysis of the arsR mutant strain revealed that ArsR seems to only control 5 genes in the genome. Furthermore, the arsR mutant strain exhibited hypersentivity to nickel, copper and cadmium and this phenotype was suppressed by mutation in arsB but not in arsC gene suggesting that overexpression of arsB is detrimental in the presence of these metals in the media.     

A mutant strain of Scenedesmus obliquus deficient in ribulose diphosphate carboxylase,cytochrome f and Photosystem II activity

The partial reactions of photosynthesis shown by strain F208, a non-photosynthetic mutant strain of Scenedesmus obliquus, have been compared with those performed by other mutant strains which lacked; Photosystem II activity (strains 11 and F131), cytochrome f (strain 50), P-700 and cytochrome f (strain F119), and P-700 (strains F139 and 199). In this respect the properties of strain F208 were those that would be expected if Photosystem II activity and cytochrome f were not present in this strain. Examination of the composition of strain F208 has shown the absence of cytochrome f in both the soluble and the membrane-bound form. The considerably lower level of plastoquinone compared to that found in the wild type is characteristic of the strains which lack Photosystem II activities.Fraction 1 protein could not be detected in extracts of strain F208 by sedimentation velocity experiments in the ultracentrifuge, and only 7% of the wild type ribulose diphosphate carboxylase activity was found after chromatography of these extracts on DEAE-cellulose.The properties of strain F208 are compared with those of the ac-20 and cr-1 strains of Chlamydomonas rheinhardi, both of which have a deficiency of ribulose diphosphate carboxylase which is considered to result from a deficiency of chloroplast ribosomes. Strain F208 resembles these strains in its abnormal chloroplast ultrastructure and its decreased levels of the RNA forms derived from the chloroplast ribosomes when compared with the wild type.Chloroplast fragments isolated from strains of S. obliquus which lacked cytochrome f (strains 50 and F208) were able to use diaminodurene and ascorbate as an electron donor to Photosystem I. Since this reaction was inhibited by mercuric salts it would appear that plastocyanin, but not cytochrome f, was involved in this electron transfer.     

Expression of the lantibiotic mersacidin in Bacillus amyloliquefaciens FZB42

Lantibiotics are small peptide antibiotics that contain the characteristic thioether amino acids lanthionine and methyllanthionine. As ribosomally synthesized peptides, lantibiotics possess biosynthetic gene clusters which contain the structural gene (lanA) as well as the other genes which are involved in lantibiotic modification (lanM, lanB, lanC, lanP), regulation (lanR, lanK), export (lanT(P)) and immunity (lanEFG). The lantibiotic mersacidin is produced by Bacillus sp. HIL Y-85,54728, which is not naturally competent.

Methodology/Principal Findings

The aim of these studies was to test if the production of mersacidin could be transferred to a naturally competent Bacillus strain employing genomic DNA of the producer strain. Bacillus amyloliquefaciens FZB42 was chosen for these experiments because it already harbors the mersacidin immunity genes. After transfer of the biosynthetic part of the gene cluster by competence transformation, production of active mersacidin was obtained from a plasmid in trans. Furthermore, comparison of several DNA sequences and biochemical testing of B. amyloliquefaciens FZB42 and B. sp. HIL Y-85,54728 showed that the producer strain of mersacidin is a member of the species B. amyloliquefaciens.

Conclusions/Significance

The lantibiotic mersacidin can be produced in B. amyloliquefaciens FZB42, which is closely related to the wild type producer strain of mersacidin. The new mersacidin producer strain enables us to use the full potential of the biosynthetic gene cluster for genetic manipulation and downstream modification approaches.     

Development and Field Performance of a Broad-Spectrum Nonviable Asporogenic Recombinant Strain of Bacillus thuringiensis with Greater Potency and UV Resistance

The main problems with Bacillus thuringiensis products for pest control are their often narrow activity spectrum, high sensitivity to UV degradation, and low cost effectiveness (high potency required). We constructed a sporulation-deficient SigK⁻ B. thuringiensis strain that expressed a chimeric cry1C/Ab gene, the product of which had high activity against various lepidopteran pests, including Spodoptera littoralis (Egyptian cotton leaf worm) and Spodoptera exigua (lesser [beet] armyworm), which are not readily controlled by other Cry δ-endotoxins. The SigK⁻ host strain carried the cry1Ac gene, the product of which is highly active against the larvae of the major pests Ostrinia nubilalis (European corn borer) and Heliothis virescens (tobacco budworm). This new strain had greater potency and a broader activity spectrum than the parent strain. The crystals produced by the asporogenic strain remained encapsulated within the cells, which protected them from UV degradation. The cry1C/Ab gene was introduced into the B. thuringiensis host via a site-specific recombination vector so that unwanted DNA was eliminated. Therefore, the final construct contained no sequences of non-B. thuringiensis origin. As the recombinant strain is a mutant blocked at late sporulation, it does not produce viable spores and therefore cannot compete with wild-type B. thuringiensis strains in the environment. It is thus a very safe biopesticide. In field trials, this new recombinant strain protected cabbage and broccoli against a pest complex under natural infestation conditions.     

Flagella proteins contribute to the production of outer membrane vesicles from Escherichia coli W3110

Gram-negative bacteria, including Escherichia coli, release outer membrane vesicles (OMVs) that are derived from the bacterial outer membrane. OMVs contribute to bacterial cell–cell communications and host–microbe interactions by delivering components to locations outside the bacterial cell. In order to explore the molecular machinery involved in OMV biogenesis, the role of a major OMV protein was examined in the production of OMVs from E. coli W3110, which is a widely used standard E. coli K-12 strain. In addition to OmpC and OmpA, which are used as marker proteins for OMVs, an analysis of E. coli W3110 OMVs revealed that they also contain abundant levels of FliC, which is also known as flagellin. A membrane-impermeable biotin-labeling reagent did not label FliC in intact OMVs, but labeled FliC in sonically disrupted OMVs, suggesting that FliC is localized in the lumen of OMV. Compared to the parental strain expressing wild-type fliC, an E. coli strain with a fliC-null mutation produced reduced amounts of OMVs based on both protein and phosphate levels. In addition, an E. coli W3110-derived strain with a null-mutation in flgK, which encodes flagellar hook-associated protein that is essential along with FliC for flagella synthesis, also produced fewer OMVs than the parental strain. Taken together, these results indicate that the ability to form flagella, including the synthesis of flagella proteins, affects the production of E. coli W3110 OMVs.     

Study ofH-2 mutations in mice VI. M523, a newK end mutant

A newH-2 mutation was found in a mouse belonging to CBA/CaLacSto (H-2 ^k ) strain and designated 523, the proposed haplotype symbol for which isH-2 ^ka . The line CBA.M523 carries this mutation and is fully congenic with the parental strain, except for the mutant site 523. The mutation 523 is located within theK- end of theH-2 gene complex. Phenotypically, it causes prompt skin graft rejection and pronounced graft-versus-host activity in strain combination CBA/Sto⇄C-BA.M523. Attempts to produce active alloantisera in the same strain combination have so far been unsuccessful.     

Expression of Human Lactoferrin in Bacteroides uniformis and its Effect on Azoxymethane-induced Aberrant Crypt Focus Formation in the Rat Colon

To express a human lactoferrin (hLF) gene in Bacteroides uniformis, a member of the anaerobic microflora in the colon, we constructed a recombinant plasmid, pVLFK, by subcloning hLF cDNA to an Escherichia coli–Bacteroides shuttle vector, pVAL-1. The plasmid pVLFKwas transferred to B. uniformis strain BU1001 by the filter mating procedure creating strain TCTK101. The lactoferrin protein in B. uniformis strain TCTK101 was detected by Western blot analysis with an anti-human lactoferrin monoclonal antibody. A culture of strain TCTK101 inhibited the growth ofE. coli strain HB101 in vitro compared to a culture of strain TCTK11, which is a B. uniformis strain-carrying plasmid pVAL-1, suggesting that the lactoferrin produced from strain TCTK101 possesses biological activity. To determine the effect of lactoferrin-producing B. uniformis on the formation of azoxymethane-induced aberrant crypt foci (ACF), putative neoplastic lesions, overnight cultures of strains TCTK11 and TCTK101 were given to rats as drinking water. The numbers of ACF and ACF having more than three crypts per focus five weeks after the beginning of the experiment significantly increased in the group treated by a culture of strain TCTK11 compared with those in the non-treated water group. However, rats treated with a culture of strain TCTK101 carrying plasmid pVLFK showed a significantly lower number of ACF than rats with a culture of strain TCTK11 (34% reduction), suggesting that hLF which is produced in a prokaryotic expression system prevents formation of ACF in the rat colon.     

Functions of poly-gamma-glutamic acid (γ-PGA) degradation genes in γ-PGA synthesis and cell morphology maintenance

Poly-γ-glutamic acid (γ-PGA) is an important biopolymer with greatly potential in industrial and medical applications. In the present study, we constructed a metabolically engineered glutamate-independent Bacillus amyloliquefaciens LL3 strain with considerable γ-PGA production, which was carried out by single, double, and triple markerless deletions of three degradation genes pgdS, ggt, and cwlO. The highest γ-PGA production (7.12 g/L) was obtained from the pgdS and cwlO double-deletion strain NK-pc, which was 93 % higher than that of wild-type LL3 strain (3.69 g/L). The triple-gene-deletion strain NK-pgc showed a 28 % decrease in γ-PGA production, leading to a yield of 2.69 g/L. Furthermore, the cell morphologies of the mutant strains were also characterized. The cell length of cwlO deletion strains NK-c and NK-pc was shorter than that of the wild-type strain, while the ggt deletion strains NK-g, NK-pg, NK-gc, and NK-pgc showed longer cell lengths. This is the first report concerning the markerless deletion of γ-PGA degradation genes to improve γ-PGA production in a glutamate-independent strain and the first observation that γ-glutamyltranspeptidase (encoded by ggt) could be involved in the inhibition of cell elongation.     

SitA contributes to the virulence of Klebsiella pneumoniae in a mouse infection model

Klebsiella pneumoniae is an opportunistic pathogen, which causes a wide range of nosocomial infections. Recently, antibiotic resistance makes K. pneumoniae infection difficult to deal with. Investigation on virulence determinants of K. pneumoniae can provide more information about pathogenesis and unveil new targets for treatment or vaccine development. In this study, SitA, a Fur-regulated divalent cation transporter, was found significantly increased when K. pneumoniae was cultured in a nutrient-limited condition. A sitA-deletion strain (ΔsitA) was created to characterize the importance of SitA in virulence. ΔsitA showed higher sensitivity toward hydroperoxide than its parental strain. In a mouse intraperitoneal infection model, the survival rate of mice infected with ΔsitA strain increased greatly when compared with that of mice infected with the parental strain, suggesting that sitA deletion attenuates the bacterial virulence in vivo. To test whether ΔsitA strain is a potential vaccine candidate, mice were immunized with inactivated bacteria and then challenged with the wild-type strain. The results showed that using ΔsitA mutant protected mice better than using the wild-type strain or the capsule-negative congenic bacteria. In summary, SitA was found being important for the growth of K. pneumoniae in vivo and deleting sitA might be a potential approach to generate vaccines against K. pneumoniae.     

Algisphaera agarilytica gen. nov., sp. nov., a novel representative of the class Phycisphaerae within the phylum Planctomycetes isolated from a marine alga

A Gram-negative, strictly aerobic, reddish-pink pigmented, motile, spherical, agar-degrading bacterium designated 06SJR6-2^T was isolated from a green coloured marine alga (Cladophora sp.). Phylogenetic analyses based on the 16S rRNA gene sequence indicated that the new strain was affiliated with the class Phycisphaerae and shared 89.2 % sequence similarity with Phycisphaera mikurensis FYK2301M01^T, which is the only validly named member of the class Phycisphaerae. The strain could be differentiated phenotypically from the recognised member of the class Phycisphaerae. The major fatty acids of strain 06SJR6-2^T were identified as C16:0, C18:1ω9c and anteiso-C15:0. Amino acid analysis of cell wall hydrolysates indicated that the novel isolate did not contain diaminopimelic acid in the cell wall. The DNA G+C content of the strain was determined to be 63.0 mol% and the major respiratory quinone was identified as menaquinone 6 (MK-6). From the distinct phylogenetic position and combination of genotypic and phenotypic characteristics, the strain is considered to represent a novel genus in the family Phycisphaeraceae, for which the name Algisphaera agarilytica gen. nov., sp. nov. is proposed. The type strain of A. agarilytica is 06SJR6-2^T (=KCTC 32482^T = NBRC 109894^T).     

Purification and characterization of α-glucosidases produced by Saccharomyces in response to three distinct maltose genes

α-Glucosidases or maltases (EC 3.2.1.20) were purified to electrophoretic homogeneity from a respective strain of Sacchromyces cerevisiae which carries a single MAL gene, either MALα, MALβ or MALγ, using gluconate-Sepharose affinity chromography and isoelectrofocusing. Of these maltases, two types of maltase were obtained from the MALγ strain, the pI values of which were 5.6 and 5.9. From the MALα and MALβ strain was obtained only one type of maltase with the pI at 5.6 which was identical to one of the maltases from the MALγ strain. These four maltases possessed the same properties, except for pI. They were monomers with molecular weights of between 66 000 and 67 000. With regard to the substrate specificity, they hydrolyzed maltose and sucrose exclusively but not α-methulglucoside nor maltooligosaccharide. They did not differ in immunological properties.     

Construction of engineered Arthrobacter simplex with improved performance for cortisone acetate biotransformation

Arthrobacter simplex 156 is a microorganism that is used for steroid drug biotransformation of cortisone acetate (CA) to prednisone acetate (PA). The enzyme 3-ketosteroid-△¹-dehydrogenase encoded by the ksdD gene plays an important role in the bioconversion process. To further improve the biotransformation efficiencies of the industrial strain, a genetic manipulation system for A. simplex 156 was developed. Additional copies of the ksdD gene under the control of the cat promoter (from pXMJ19) were transferred into the strain A. simplex 156 and integrated into the 16S rDNA sites, yielding a series of recombinant strains. One of these recombinant strains, designated A. simplex M158, exhibited superior properties for CA biotransformation. At the substrate concentration of 83.6 g/l, the highest PA production of the recombinant strain reached 66.7 g/l, which is approximately 32.9 % higher than that of wild-type strains, and the incubation time for CA to PA bioconversion was reduced by 20 h. Southern blotting analysis of the recombinant strain indicated two copies of deregulated ksdD genes were integrated into the 16S rDNA sites, which means two of five 16S rRNA operons were insertionally disrupted in the recombinant strain. However, the disruption of the two 16S rRNA operons did not affect the growth rate of the recombinant strain, which survived and thrived under desired conditions. In addition, the new strain was genetically stable for more than 100 generations without the use of antibiotics for selection. These superior characteristics make the new strain more suitable than the wild-type strain for PA production.     

Metabolic engineering of Pseudomonas fluorescens for the production of vanillin from ferulic acid

Vanillin is one of the most important flavors in the food industry and there is great interest in its production through biotechnological processes starting from natural substrates such as ferulic acid. Among bacteria, recombinant Escherichia coli strains are the most efficient vanillin producers, whereas Pseudomonas spp. strains, although possessing a broader metabolic versatility, rapidly metabolize various phenolic compounds including vanillin. In order to develop a robust Pseudomonas strain that can produce vanillin in high yields and at high productivity, the vanillin dehydrogenase (vdh)-encoding gene of Pseudomonas fluorescens BF13 strain was inactivated via targeted mutagenesis. The results demonstrated that engineered derivatives of strain BF13 accumulate vanillin if inactivation of vdh is associated with concurrent expression of structural genes for feruloyl-CoA synthetase (fcs) and hydratase/aldolase (ech) from a low-copy plasmid. The conversion of ferulic acid to vanillin was enhanced by optimization of growth conditions, growth phase and parameters of the bioconversion process. The developed strain produced up to 8.41 mM vanillin, which is the highest final titer of vanillin produced by a Pseudomonas strain to date and opens new perspectives in the use of bacterial biocatalysts for biotechnological production of vanillin from agro-industrial wastes which contain ferulic acid.     

Role of Secondary Metabolites in Establishment of the Mutualistic Partnership between Xenorhabdus nematophila and the Entomopathogenic Nematode Steinernema carpocapsae

Xenorhabdus nematophila engages in a mutualistic partnership with the nematode Steinernema carpocapsae, which invades insects, migrates through the gut, and penetrates into the hemocoel (body cavity). We showed previously that during invasion of Manduca sexta, the gut microbe Staphylococcus saprophyticus appeared transiently in the hemocoel, while Enterococcus faecalis proliferated as X. nematophila became dominant. X. nematophila produces diverse secondary metabolites, including the major water-soluble antimicrobial xenocoumacin. Here, we study the role of X. nematophila antimicrobials in interspecies competition under biologically relevant conditions using strains lacking either xenocoumacin (ΔxcnKL strain), xenocoumacin and the newly discovered antibiotic F (ΔxcnKL:F strain), or all ngrA-derived secondary metabolites (ngrA strain). Competition experiments were performed in Grace''s insect medium, which is based on lepidopteran hemolymph. S. saprophyticus was eliminated when inoculated into growing cultures of either the ΔxcnKL strain or ΔxcnKL:F strain but grew in the presence of the ngrA strain, indicating that ngrA-derived antimicrobials, excluding xenocoumacin or antibiotic F, were required to eliminate the competitor. In contrast, S. saprophyticus was eliminated when coinjected into M. sexta with either the ΔxcnKL or ngrA strain, indicating that ngrA-derived antimicrobials were not required to eliminate the competitor in vivo. E. faecalis growth was facilitated when coinjected with either of the mutant strains. Furthermore, nematode reproduction in M. sexta naturally infected with infective juveniles colonized with the ngrA strain was markedly reduced relative to the level of reproduction when infective juveniles were colonized with the wild-type strain. These findings provide new insights into interspecies competition in a host environment and suggest that ngrA-derived compounds serve as signals for in vivo nematode reproduction.     

Asymbiotic Acetylene Reduction by a Fast-Growing Cowpea Rhizobium Strain with Nitrogenase Structural Genes Located on a Symbiotic Plasmid

A procedure was designed which enabled the detection of ex planta nitrogenase activity in the fast-growing cowpea Rhizobium strain IHP100. Nitrogenase activity in agar culture under air occurred at a rate similar to that found for Bradyrhizobium strain CB756 but lower than that for Rhizobium strain ORS571. Hybridization studies showed that both nod and nif genes were located on a 410-kilobase Sym plasmid in strain IHP100.     

Grimontia indica AK16T,sp. nov., Isolated from a Seawater Sample Reports the Presence of Pathogenic Genes Similar to Vibrio Genus

Grimontia indica strain AK16^T sp. nov. is the type strain of G. indica sp. nov. a new species within the genus Grimontia. This strain, whose genome is described here, was isolated from seawater sample collected from southeast coast of Palk Bay, India. G. indica AK16^T is a Gram-negative, facultative aerobic rod shaped bacterium. There are only two other strains in the genus Grimontia one of which, Grimontia hollisae CIP 101886^T, is a reported human pathogen isolated from human stool sample while the other, ‘Grimontia marina IMCC5001^T’, was isolated from a seawater sample. As compared to the pathogenic strain Grimontia hollisae CIP 101886^T, the strain AK16^T lacks some genes for pathogenesis like the accessory colonization factors AcfA and AcfD, which are required for the colonization of the bacterium in the host body. While it carries some pathogenesis genes like OmpU, which are related to pathogenesis of Vibrio strains. This suggests that the life cycle of AK16^T may include some pathogenic interactions with marine animal(s), or it may be an opportunistic pathogen. Study of the Grimontia genus is important because of the severe pathogenic traits exhibited by a member of the genus with only three species reported in total. The study will provide some vital information which may be useful in future clinical studies on the genus.     

In vivo characterization of a Toxoplasma gondii strain TgCatJpTy1/k-3 isolated from a stray cat in Japan

The Toxoplasma gondii strain TgCatJpTy1/k-3 (K-3), isolated from a stray cat in Tokyo, Japan, is categorized as a type II genotype. Since the K-3 strain is empirically known to form relatively larger cysts and exhibit weak pathogenesis in a mouse, it could serve as a useful model organism to study chronic T. gondii infection in the host. However, a detailed biological characterization of this strain had not been performed. In this study, we thoroughly assessed the K-3 strain in vivo using a mouse model. Tests indicated that pathogenicity of the K-3 strain was lower than that of the PLK strain, a clonal laboratory strain with a moderately pathogenic type II genotype. Further, cyst sizes of the K-3 strain were significantly larger than those of the PLK strain. Interestingly, K-3 cyst sizes in T. gondii-resistant ICR mice were larger than those in T. gondii-susceptible C57BL/6N mice.Our study suggests that the K-3 strain is suitable to study T. gondii cystogenesis and chronic infection, which are currently difficult to analyze using cell-adopted T. gondii strains.