The aim of this work is the taxonomic characterization of three biosurfactant-producing bacterial isolates from the Churince system at Cuatro Ciénegas Basin (CCB) in the Mexican State of Coahuila, and the study of the possible role of biosurfactant production in their ecology and evolution. We determined that these isolates belong to a Pseudomonas koreensis lineage endemic to CCB, using standard taxonomical techniques, phylogenetic analysis of three chromosomal loci and phenotypic characterization. This new lineage has the distinct capacity to produce a biosurfactant when compared with previously reported P. koreensis isolates recovered from agricultural soils in Korea. We present evidence suggesting that the biosurfactant secreted by CCB P. koreensis strains is involved in their ability to compete with a CCB Exiguobacterium aurantiacum strain (m5-66) used as a model organism in competition experiments. Furthermore, the ethyl acetate extract of culture supernatant of CCB P. koreensis strains results in growth inhibition not only of E. aurantiacum m5-66, but also of a Bacillus subtilis type strain (ATCC6633). Based on these results we propose that the production of biosurfactant could be of ecological importance and could play a role in the separation of the P. koreensis CCB lineage. 相似文献
Mitochondrial (mt) genes and genomes are among the major sources of data for evolutionary studies in birds. This places mitogenomic studies in birds at the core of intense debates in avian evolutionary biology. Indeed, complete mt genomes are actively been used to unveil the phylogenetic relationships among major orders, whereas single genes (e.g., cytochrome c oxidase I [COX1]) are considered standard for species identification and defining species boundaries (DNA barcoding). In this investigation, we study the time of origin and evolutionary relationships among Neoaves orders using complete mt genomes. First, we were able to solve polytomies previously observed at the deep nodes of the Neoaves phylogeny by analyzing 80 mt genomes, including 17 new sequences reported in this investigation. As an example, we found evidence indicating that columbiforms and charadriforms are sister groups. Overall, our analyses indicate that by improving the taxonomic sampling, complete mt genomes can solve the evolutionary relationships among major bird groups. Second, we used our phylogenetic hypotheses to estimate the time of origin of major avian orders as a way to test if their diversification took place prior to the Cretaceous/Tertiary (K/T) boundary. Such timetrees were estimated using several molecular dating approaches and conservative calibration points. Whereas we found time estimates slightly younger than those reported by others, most of the major orders originated prior to the K/T boundary. Finally, we used our timetrees to estimate the rate of evolution of each mt gene. We found great variation on the mutation rates among mt genes and within different bird groups. COX1 was the gene with less variation among Neoaves orders and the one with the least amount of rate heterogeneity across lineages. Such findings support the choice of COX 1 among mt genes as target for developing DNA barcoding approaches in birds. 相似文献
The oomycete Phytophthora capsici causes wilting disease in chilli pepper and another solanaceous plants, with important economic consequences. Although much investigation has been conducted about this pathogen, little is still known about which of its proteins are involved in the infection process. In this study, the bioassay‐guided fractionation of the secretome of P. capsici resulted in the purification of a phytotoxic protein fraction designated as p47f, capable of inducing wilting and necrosis on leaves of Capsicum chinense Jacq, and having a 47 kDa polypeptide with proteolytic activity as the major component. The isolated p47f fraction induced DNA degradation and decreased cell survival of C. chinense cell suspension culture. Sequencing of p47f indicated the presence of 15 proteins, which could be grouped into seven classes including a protease group, cell wall remodelling proteins and the transglutaminase elicitor M81D, among others. This is the first report of P. capsici secreting proteins that modulate cell responses mediated by ROS in the host. 相似文献
Bioaerosols are transported from warm regions and lower latitudes of the planet to colder regions and higher latitudes, such as the Chilean Patagonia. The role of bioaerosols deposition in remote lake ecosystems is a potentially important process, but it has not yet been fully studied. The aim of this study was to detect and characterize potentially pathogenic viable microorganisms in bioaerosols in a pristine area. Samples were collected from the air, at three remote lakes in the Chilean Patagonia, using a sterile filtration system equipped with 0.2-μm-pore-size nitrocellulose filters. The bacterial community present in bioaerosols was studied using scanning electron microscopy (SEM) and denaturing gradient gel electrophoresis. Isolates were identified and characterized for phenotypic and 16S rDNA analysis and antibiotic resistance. SEM observations of samples from each lake showed the presence of bacteria with different morphologies, and after culturing, the identification results revealed that they were strains of Acinetobacter, Alcaligenes, Edwarsiella, Pseudomonas, Burklolderia, Moraxella, Sphingomonas and CDC NO-1. CDC NO-1, uncommonly isolated worldwide, stands out from the rest of the isolates because it is a rarely found bacterium so far associated with dog and cat bites and was found at two out of three pristine lakes studied (Alto and Verde). This work demonstrates, for the first time, the presence of CDC NO-1, a clinically important Gram-negative microorganism, in bioaerosols and first report of CDC-NO1 isolation in Chile. Besides its presence in remote lakes, its antibiotic resistance is worth mentioning. 相似文献
Deposition of suspended sediments andtheir associated nutrients were estimated during theflood event of 1995 in the seasonally flooded forestsof the Mapire and Caura Rivers, two black-watertributaries of lower Orinoco, and on two islands ofthis white-water river. The deposition spanned a widerange from 0.07 kg m–2 in the depositional barforests of the Mapire River to 73.60 kg m–2 onthe flooded forests of the Orinoco Island site calledJarizo. This variation is associated with the dynamicnature of sediment mobilization, transport anddeposition, as well as with the different geomorphicenvironments and erosion processes upstream from thestudy sites. The deposited sediment in all the studyareas was highly quartzitic with a relatively highcontent of kaolinite and goethite. Only in thesediment of the Orinoco Islands was mica (illite)identified in a relatively high proportion. Thesemineralogical results reflect the intense weatheringprocesses in the catchment areas of the study rivers.The chemical composition of the deposited sedimentsshowed a great variability among the different studyareas, which is in part related to the mineralcomposition of the sediments and their particle sizedistribution. The highest concentrations of K, Caand Mg were found on the clay sediments of the Orinocoagricultural island. The total amount of depositednutrients varied over a wide range, which isinfluenced by the amount of deposited sediments. Inthe Jarizo Island site of lower Orinoco were depositedthe largest amount of nutrients. In the floodedforests of the Mapire River, the nutrient contributionby the deposited sediments to the nutrient cycling isrelatively low in the depositional-bar forests andpractically nonexistent in the forests sites onterraces. 相似文献
The genomes of Listeria spp. encode all but one of 25 enzymes required for the biosynthesis of adenosylcobalamin (AdoCbl; coenzyme B12). Notably, all Listeria genomes lack CobT, the nicotinamide mononucleotide:5,6‐dimethylbenzimidazole (DMB) phosphoribosyltransferase (EC 2.4.2.21) enzyme that synthesizes the unique α‐linked nucleotide N1‐(5‐phospho‐α‐d ‐ribosyl)‐DMB (α‐ribazole‐5′‐P, α‐RP), a precursor of AdoCbl. We have uncovered a new pathway for the synthesis of α‐RP in Listeria innocua that circumvents the lack of CobT. The cblT and cblS genes (locus tags lin1153 and lin1110) of L. innocua encode an α‐ribazole (α‐R) transporter and an α‐R kinase respectively. Results from in vivo experiments indicate that L. innocua depends on CblT and CblS activities to salvage exogenous α‐R, allowing conversion of the incomplete corrinoid cobinamide (Cbi) into AdoCbl. Expression of the L. innocua cblT and cblS genes restored AdoCbl synthesis from Cbi and α‐R in a Salmonella enterica cobT strain. LinCblT transported α‐R across the cell membrane, but not α‐RP or DMB. UV‐visible spectroscopy and mass spectrometry data identified α‐RP as the product of the ATP‐dependent α‐R kinase activity of LinCblS. Bioinformatics analyses suggest that α‐R salvaging occurs in important Gram‐positive human pathogens. 相似文献
The previous deletion of the cytoplasmic components of the phosphotransferase system (PTS) in Escherichia coli JM101 resulted in the PTS− derivative strain PB11 with severely impaired growth capability in glucose as the sole carbon source. Previous adaptive laboratory evolution (ALE) experiment led to select a fast-growing strain named PB12 from PB11. Comparative genome analysis of PB12 showed a chromosomal deletion, which result in the loss of several genes including rppH which codes for the RNA pyrophosphohydrolase RppH, involved in the preparation of hundreds of mRNAs for further degradation by RNase E. Previous inactivation of rppH in PB11 (PB11rppH−) improved significantly its growing capabilities and increased several mRNAs respect its parental strain PB11. These previous results led to propose to the PB11rppH− mutant as an intermediate between PB11 and PB12 strains merged during the early ALE experiment. In this contribution, we report the metabolic response to the PTS− and rppH− mutations in the deep of a proteomic approach to understanding the relevance of rppH− phenotype during an ALE experiment. Differentially upregulated proteins between the wild-type JM101/PB11, PB11/PB11rppH−, and PB11/PB12 comparisons led to identifying 45 proteins between strain comparisons. Downregulated or upregulated proteins in PB11rppH− were found expressed at an intermediate level with respect to PB11 and PB12. Many of these proteins were found involved in non-previously metabolic traits reported in the study of the PTS− strains, including glucose, amino acids, ribose transport; amino acid biosynthesis; NAD biosynthesis/salvage pathway, biosynthesis of Ac-CoA precursors; detoxification and degradation pathways; stress response; protein synthesis; and possible mutator activities between comparisons. No changes were found in the expression of galactose permease GalP, previously proposed as the primary glucose transporter in the absence of PTS selected by the PTS− derivatives during the ALE experiment. This result suggests that the evolving PTS− population selected other transporters such as LamB, MglB, and ManX instead of GalP for glucose uptake during the early ALE experiment. Analysis of the biological relevance of the metabolic traits developed by the studied strains provided valuable information to understand the relevance of the rppH− mutation in the PTS− background during an ALE experiment as a strategy for the selection of valuable phenotypes for metabolic engineering purposes.
The proteolytic enzyme stromelysin-1 is a member of the family of matrix metalloproteinases and is believed to play a role in pathological conditions such as arthritis and tumor invasion. Stromelysin-1 is synthesized as a pro-enzyme that is activated by removal of an N-terminal prodomain. The active enzyme contains a catalytic domain and a C-terminal hemopexin domain believed to participate in macromolecular substrate recognition. We have determined the three-dimensional structures of both a C-truncated form of the proenzyme and an inhibited complex of the catalytic domain by X-ray diffraction analysis. The catalytic core is very similar in the two forms and is similar to the homologous domain in fibroblast and neutrophil collagenases, as well as to the stromelysin structure determined by NMR. The prodomain is a separate folding unit containing three alpha-helices and an extended peptide that lies in the active site of the enzyme. Surprisingly, the amino-to-carboxyl direction of this peptide chain is opposite to that adopted by the inhibitor and by previously reported inhibitors of collagenase. Comparison of the active site of stromelysin with that of thermolysin reveals that most of the residues proposed to play significant roles in the enzymatic mechanism of thermolysin have equivalents in stromelysin, but that three residues implicated in the catalytic mechanism of thermolysin are not represented in stromelysin. 相似文献
The role of the enzymes uridine-5'-diphospho-(UDP) glucose pyrophosphorylase and UDP galactose 4-epimerase in exopolysaccharide production of Gal− ropy and non-ropy strains of Streptococcus thermophilus in a batch culture was investigated. Growth of the ropy and non-ropy strains was accompanied by total release of the galactose moiety from lactose hydrolysis in modified Bellinker broth with lactose as the only carbon source. This was associated with a greater exopolysaccharide production by the ropy strain. The polymer produced by both strains in cultures with lactose or glucose as carbon sources contained glucose, galactose and rhamnose, indicating that glucose was used as a carbon source for bacterial growth and for exopolysaccharide formation. UDP-glucose pyrophosphorylase activity was associated with polysaccharide production during the first 12 h in a 20 h culture in the ropy strain, but not in the non-ropy strain. UDP-galactose 4-epimerase was not associated with exopolysaccharide synthesis in any strain. The evidence presented suggests that the glucose moiety from lactose hydrolysis is the source of sugar for heteropolysaccharide synthesis, due to a high UDP-glucose pyrophosphorylase activity. 相似文献