Comparative genomic analysis of Acinetobacter strains isolated from murine colonic crypts. - Related Documents




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836501.0000Comparative genomic analysis of Acinetobacter strains isolated from murine colonic crypts. BACKGROUND: A restricted set of aerobic bacteria dominated by the Acinetobacter genus was identified in murine intestinal colonic crypts. The vicinity of such bacteria with intestinal stem cells could indicate that they protect the crypt against cytotoxic and genotoxic signals. Genome analyses of these bacteria were performed to better appreciate their biodegradative capacities. RESULTS: Two taxonomically different clusters of Acinetobacter were isolated from murine proximal colonic crypts, one was identified as A. modestus and the other as A. radioresistens. Their identification was performed through biochemical parameters and housekeeping gene sequencing. After selection of one strain of each cluster (A. modestus CM11G and A. radioresistens CM38.2), comparative genomic analysis was performed on whole-genome sequencing data. The antibiotic resistance pattern of these two strains is different, in line with the many genes involved in resistance to heavy metals identified in both genomes. Moreover whereas the operon benABCDE involved in benzoate metabolism is encoded by the two genomes, the operon antABC encoding the anthranilate dioxygenase, and the phenol hydroxylase gene cluster are absent in the A. modestus genomic sequence, indicating that the two strains have different capacities to metabolize xenobiotics. A common feature of the two strains is the presence of a type IV pili system, and the presence of genes encoding proteins pertaining to secretion systems such as Type I and Type II secretion systems. CONCLUSIONS: Our comparative genomic analysis revealed that different Acinetobacter isolated from the same biological niche, even if they share a large majority of genes, possess unique features that could play a specific role in the protection of the intestinal crypt.201728697749
838410.9993In vivo function and comparative genomic analyses of the Drosophila gut microbiota identify candidate symbiosis factors. Symbiosis is often characterized by co-evolutionary changes in the genomes of the partners involved. An understanding of these changes can provide insight into the nature of the relationship, including the mechanisms that initiate and maintain an association between organisms. In this study we examined the genome sequences of bacteria isolated from the Drosophila melanogaster gut with the objective of identifying genes that are important for function in the host. We compared microbiota isolates with con-specific or closely related bacterial species isolated from non-fly environments. First the phenotype of germ-free Drosophila (axenic flies) was compared to that of flies colonized with specific bacteria (gnotobiotic flies) as a measure of symbiotic function. Non-fly isolates were functionally distinct from bacteria isolated from flies, conferring slower development and an altered nutrient profile in the host, traits known to be microbiota-dependent. Comparative genomic methods were next employed to identify putative symbiosis factors: genes found in bacteria that restore microbiota-dependent traits to gnotobiotic flies, but absent from those that do not. Factors identified include riboflavin synthesis and stress resistance. We also used a phylogenomic approach to identify protein coding genes for which fly-isolate sequences were more similar to each other than to other sequences, reasoning that these genes may have a shared function unique to the fly environment. This method identified genes in Acetobacter species that cluster in two distinct genomic loci: one predicted to be involved in oxidative stress detoxification and another encoding an efflux pump. In summary, we leveraged genomic and in vivo functional comparisons to identify candidate traits that distinguish symbiotic bacteria. These candidates can serve as the basis for further work investigating the genetic requirements of bacteria for function and persistence in the Drosophila gut.201425408687
838720.9993Construction and Analysis of Two Genome-Scale Deletion Libraries for Bacillus subtilis. A systems-level understanding of Gram-positive bacteria is important from both an environmental and health perspective and is most easily obtained when high-quality, validated genomic resources are available. To this end, we constructed two ordered, barcoded, erythromycin-resistance- and kanamycin-resistance-marked single-gene deletion libraries of the Gram-positive model organism, Bacillus subtilis. The libraries comprise 3,968 and 3,970 genes, respectively, and overlap in all but four genes. Using these libraries, we update the set of essential genes known for this organism, provide a comprehensive compendium of B. subtilis auxotrophic genes, and identify genes required for utilizing specific carbon and nitrogen sources, as well as those required for growth at low temperature. We report the identification of enzymes catalyzing several missing steps in amino acid biosynthesis. Finally, we describe a suite of high-throughput phenotyping methodologies and apply them to provide a genome-wide analysis of competence and sporulation. Altogether, we provide versatile resources for studying gene function and pathway and network architecture in Gram-positive bacteria.201728189581
838630.9992Molecular evolution and population genetics of glutamate decarboxylase acid resistance pathway in lactic acid bacteria. Glutamate decarboxylase (GAD) pathway (GDP) is a major acid resistance mechanism enabling microorganisms' survival in low pH environments. We aimed to study the molecular evolution and population genetics of GDP in Lactic Acid Bacteria (LAB) to understand evolutionary processes shaping adaptation to acidic environments comparing species where the GDP genes are organized in an operon structure (Levilactobacillus brevis) versus lack of an operon structure (Lactiplantibacillus plantarum). Within species molecular population genetic analyses of GDP genes in L. brevis and L. plantarum sampled from diverse fermented food and other environments showed abundant synonymous and non-synonymous nucleotide diversity, mostly driven by low frequency changes, distributed throughout the coding regions for all genes in both species. GAD genes showed higher level of replacement polymorphism compared to transporter genes (gadC and YjeM) for both species, and GAD genes that are outside of an operon structure showed even higher level of replacement polymorphism. Population genetic tests suggest negative selection against replacement changes in all genes. Molecular structure and amino acid characteristics analyses showed that in none of the GDP genes replacement changes alter 3D structure or charge distribution supporting negative selection against non-conservative amino acid changes. Phylogenetic and between species divergence analyses suggested adaptive protein evolution on GDP genes comparing phylogenetically distant species, but conservative evolution comparing closely related species. GDP genes within an operon structure showed slower molecular evolution and higher conservation. All GAD and transporter genes showed high codon usage bias in examined LAB species suggesting high expression and utilization of acid resistance genes. Substantial discordances between species, GAD, and transporter gene tree topologies were observed suggesting molecular evolution of GDP genes do not follow speciation events. Distribution of operon structure on the species tree suggested multiple independent gain or loss of operon structure in LABs. In conclusion, GDP genes in LABs exhibit a dynamic molecular evolutionary history shaped by gene loss, gene transfer, negative and positive selection to maintain its active role in acid resistance mechanism, and enable organisms to thrive in acidic environments.202336777729
434740.9992Going through phages: a computational approach to revealing the role of prophage in Staphylococcus aureus. Prophages have important roles in virulence, antibiotic resistance, and genome evolution in Staphylococcus aureus . Rapid growth in the number of sequenced S. aureus genomes allows for an investigation of prophage sequences at an unprecedented scale. We developed a novel computational pipeline for phage discovery and annotation. We combined PhiSpy, a phage discovery tool, with VGAS and PROKKA, genome annotation tools to detect and analyse prophage sequences in nearly 10 011  S . aureus genomes, discovering thousands of putative prophage sequences with genes encoding virulence factors and antibiotic resistance. To our knowledge, this is the first large-scale application of PhiSpy on a large-scale set of genomes (10 011  S . aureus ). Determining the presence of virulence and resistance encoding genes in prophage has implications for the potential transfer of these genes/functions to other bacteria via transduction and thus can provide insight into the evolution and spread of these genes/functions between bacterial strains. While the phage we have identified may be known, these phages were not necessarily known or characterized in S. aureus and the clustering and comparison we did for phage based on their gene content is novel. Moreover, the reporting of these genes with the S. aureus genomes is novel.202337424556
837850.9992Genome mining reveals unlocked bioactive potential of marine Gram-negative bacteria. BACKGROUND: Antibiotic resistance in bacteria spreads quickly, overtaking the pace at which new compounds are discovered and this emphasizes the immediate need to discover new compounds for control of infectious diseases. Terrestrial bacteria have for decades been investigated as a source of bioactive compounds leading to successful applications in pharmaceutical and biotech industries. Marine bacteria have so far not been exploited to the same extent; however, they are believed to harbor a multitude of novel bioactive chemistry. To explore this potential, genomes of 21 marine Alpha- and Gammaproteobacteria collected during the Galathea 3 expedition were sequenced and mined for natural product encoding gene clusters. RESULTS: Independently of genome size, bacteria of all tested genera carried a large number of clusters encoding different potential bioactivities, especially within the Vibrionaceae and Pseudoalteromonadaceae families. A very high potential was identified in pigmented pseudoalteromonads with up to 20 clusters in a single strain, mostly NRPSs and NRPS-PKS hybrids. Furthermore, regulatory elements in bioactivity-related pathways including chitin metabolism, quorum sensing and iron scavenging systems were investigated both in silico and in vitro. Genes with siderophore function were identified in 50% of the strains, however, all but one harboured the ferric-uptake-regulator gene. Genes encoding the syntethase of acylated homoserine lactones were found in Roseobacter-clade bacteria, but not in the Vibrionaceae strains and only in one Pseudoalteromonas strains. The understanding and manipulation of these elements can help in the discovery and production of new compounds never identified under regular laboratory cultivation conditions. High chitinolytic potential was demonstrated and verified for Vibrio and Pseudoalteromonas species that commonly live in close association with eukaryotic organisms in the environment. Chitin regulation by the ChiS histidine-kinase seems to be a general trait of the Vibrionaceae family, however it is absent in the Pseudomonadaceae. Hence, the degree to which chitin influences secondary metabolism in marine bacteria is not known. CONCLUSIONS: Utilizing the rapidly developing sequencing technologies and software tools in combination with phenotypic in vitro assays, we demonstrated the high bioactive potential of marine bacteria in an efficient, straightforward manner - an approach that will facilitate natural product discovery in the future.201525879706
837760.9992Genome-Wide Association Analyses in the Model Rhizobium Ensifer meliloti. Genome-wide association studies (GWAS) can identify genetic variants responsible for naturally occurring and quantitative phenotypic variation. Association studies therefore provide a powerful complement to approaches that rely on de novo mutations for characterizing gene function. Although bacteria should be amenable to GWAS, few GWAS have been conducted on bacteria, and the extent to which nonindependence among genomic variants (e.g., linkage disequilibrium [LD]) and the genetic architecture of phenotypic traits will affect GWAS performance is unclear. We apply association analyses to identify candidate genes underlying variation in 20 biochemical, growth, and symbiotic phenotypes among 153 strains of Ensifer meliloti For 11 traits, we find genotype-phenotype associations that are stronger than expected by chance, with the candidates in relatively small linkage groups, indicating that LD does not preclude resolving association candidates to relatively small genomic regions. The significant candidates show an enrichment for nucleotide polymorphisms (SNPs) over gene presence-absence variation (PAV), and for five traits, candidates are enriched in large linkage groups, a possible signature of epistasis. Many of the variants most strongly associated with symbiosis phenotypes were in genes previously identified as being involved in nitrogen fixation or nodulation. For other traits, apparently strong associations were not stronger than the range of associations detected in permuted data. In sum, our data show that GWAS in bacteria may be a powerful tool for characterizing genetic architecture and identifying genes responsible for phenotypic variation. However, careful evaluation of candidates is necessary to avoid false signals of association.IMPORTANCE Genome-wide association analyses are a powerful approach for identifying gene function. These analyses are becoming commonplace in studies of humans, domesticated animals, and crop plants but have rarely been conducted in bacteria. We applied association analyses to 20 traits measured in Ensifer meliloti, an agriculturally and ecologically important bacterium because it fixes nitrogen when in symbiosis with leguminous plants. We identified candidate alleles and gene presence-absence variants underlying variation in symbiosis traits, antibiotic resistance, and use of various carbon sources; some of these candidates are in genes previously known to affect these traits whereas others were in genes that have not been well characterized. Our results point to the potential power of association analyses in bacteria, but also to the need to carefully evaluate the potential for false associations.201830355664
633870.9992Transcriptome Analysis of the Intracellular Facultative Pathogen Piscirickettsia salmonis: Expression of Putative Groups of Genes Associated with Virulence and Iron Metabolism. The intracellular facultative bacteria Piscirickettsia salmonis is one of the most important pathogens of the Chilean aquaculture. However, there is a lack of information regarding the whole genomic transcriptional response according to different extracellular environments. We used next generation sequencing (NGS) of RNA (RNA-seq) to study the whole transcriptome of an isolate of P. salmonis (FAVET-INBIOGEN) using a cell line culture and a modified cell-free liquid medium, with or without iron supplementation. This was done in order to obtain information about the factors there are involved in virulence and iron acquisition. First, the isolate was grown in the Sf21 cell line; then, the bacteria were cultured into a cell-free liquid medium supplemented or not with iron. We identified in the transcriptome, genes associated with type IV secretion systems, genes related to flagellar structure assembly, several proteases and sigma factors, and genes related to the development of drug resistance. Additionally, we identified for the first time several iron-metabolism associated genes including at least two iron uptake pathways (ferrous iron and ferric iron uptake) that are actually expressed in the different conditions analyzed. We further describe putative genes that are related with the use and storage of iron in the bacteria, which have not been previously described. Several sets of genes related to virulence were expressed in both the cell line and cell-free culture media (for example those related to flagellar structure; such as basal body, MS-ring, C-ring, proximal and distal rod, and filament), which may play roles in other basic processes rather than been restricted to virulence.201628033422
438180.9992Specific Gene Loci of Clinical Pseudomonas putida Isolates. Pseudomonas putida are ubiquitous inhabitants of soils and clinical isolates of this species have been seldom described. Clinical isolates show significant variability in their ability to cause damage to hosts because some of them are able to modulate the host's immune response. In the current study, comparisons between the genomes of different clinical and environmental strains of P. putida were done to identify genetic clusters shared by clinical isolates that are not present in environmental isolates. We show that in clinical strains specific genes are mostly present on transposons, and that this set of genes exhibit high identity with genes found in pathogens and opportunistic pathogens. The set of genes prevalent in P. putida clinical isolates, and absent in environmental isolates, are related with survival under oxidative stress conditions, resistance against biocides, amino acid metabolism and toxin/antitoxin (TA) systems. This set of functions have influence in colonization and survival within human tissues, since they avoid host immune response or enhance stress resistance. An in depth bioinformatic analysis was also carried out to identify genetic clusters that are exclusive to each of the clinical isolates and that correlate with phenotypical differences between them, a secretion system type III-like was found in one of these clinical strains, a determinant of pathogenicity in Gram-negative bacteria.201626820467
634790.9992Bifidobacterium adolescentis is resistant to pyrazinamide, isoniazid, and streptomycin. The current study aims to understand the resistance of Bifidobacterium adolescentis to different anti-tubercular drugs (first-line oral tuberculosis drugs). The bacteria were grown with anti-tubercular drugs such as isoniazid, pyrazinamide, and streptomycin to better understand the resistance phenomena. It was found that even at tenfold higher concentrations, growth rates remained unchanged. In addition, a small number of bacteria were found to aggregate strongly, a property that protects against the toxicity of the drug. Further FE-SEM (Field Emission Scanning Electron Microscopy) analysis revealed that some bacteria became excessively long, elongated, and protruded on the surface. Size scattering analysis confirmed the presence of bifidobacteria in the size range of 1.0-100 μm. After whole genome sequence analysis, certain mutations were found in the relevant gene. In vitro, foam formation and growth in the presence of H(2)O(2) and HPLC (High Performance Liquid Chromatography) studies provide additional evidence for the presence of catalase. According to RAST (Rapid Annotation Using Subsystems Technology) annotation and CARD (Comprehensive Antibiotic Resistance Database analysis), there were not many components in the genome that were resistant to antibiotics. Whole genome sequence (WGS) analysis does not show the presence of bacteriocins and antibiotic resistance genes, but few hypothetical proteins were observed. 3D structure and docking studies suggest their interaction with specific ligands.202439609447
4375100.9992Evidence of a large novel gene pool associated with prokaryotic genomic islands. Microbial genes that are "novel" (no detectable homologs in other species) have become of increasing interest as environmental sampling suggests that there are many more such novel genes in yet-to-be-cultured microorganisms. By analyzing known microbial genomic islands and prophages, we developed criteria for systematic identification of putative genomic islands (clusters of genes of probable horizontal origin in a prokaryotic genome) in 63 prokaryotic genomes, and then characterized the distribution of novel genes and other features. All but a few of the genomes examined contained significantly higher proportions of novel genes in their predicted genomic islands compared with the rest of their genome (Paired t test = 4.43E-14 to 1.27E-18, depending on method). Moreover, the reverse observation (i.e., higher proportions of novel genes outside of islands) never reached statistical significance in any organism examined. We show that this higher proportion of novel genes in predicted genomic islands is not due to less accurate gene prediction in genomic island regions, but likely reflects a genuine increase in novel genes in these regions for both bacteria and archaea. This represents the first comprehensive analysis of novel genes in prokaryotic genomic islands and provides clues regarding the origin of novel genes. Our collective results imply that there are different gene pools associated with recently horizontally transmitted genomic regions versus regions that are primarily vertically inherited. Moreover, there are more novel genes within the gene pool associated with genomic islands. Since genomic islands are frequently associated with a particular microbial adaptation, such as antibiotic resistance, pathogen virulence, or metal resistance, this suggests that microbes may have access to a larger "arsenal" of novel genes for adaptation than previously thought.200516299586
4373110.9992Plasmids of psychrophilic and psychrotolerant bacteria and their role in adaptation to cold environments. Extremely cold environments are a challenge for all organisms. They are mostly inhabited by psychrophilic and psychrotolerant bacteria, which employ various strategies to cope with the cold. Such harsh environments are often highly vulnerable to the influence of external factors and may undergo frequent dynamic changes. The rapid adjustment of bacteria to changing environmental conditions is crucial for their survival. Such "short-term" evolution is often enabled by plasmids-extrachromosomal replicons that represent major players in horizontal gene transfer. The genomic sequences of thousands of microorganisms, including those of many cold-active bacteria have been obtained over the last decade, but the collected data have yet to be thoroughly analyzed. This report describes the results of a meta-analysis of the NCBI sequence databases to identify and characterize plasmids of psychrophilic and psychrotolerant bacteria. We have performed in-depth analyses of 66 plasmids, almost half of which are cryptic replicons not exceeding 10 kb in size. Our analyses of the larger plasmids revealed the presence of numerous genes, which may increase the phenotypic flexibility of their host strains. These genes encode enzymes possibly involved in (i) protection against cold and ultraviolet radiation, (ii) scavenging of reactive oxygen species, (iii) metabolism of amino acids, carbohydrates, nucleotides and lipids, (iv) energy production and conversion, (v) utilization of toxic organic compounds (e.g., naphthalene), and (vi) resistance to heavy metals, metalloids and antibiotics. Some of the plasmids also contain type II restriction-modification systems, which are involved in both plasmid stabilization and protection against foreign DNA. Moreover, approx. 50% of the analyzed plasmids carry genetic modules responsible for conjugal transfer or mobilization for transfer, which may facilitate the spread of these replicons among various bacteria, including across species boundaries.201425426110
4344120.9992Phenetic Comparison of Prokaryotic Genomes Using k-mers. Bacterial genomics studies are getting more extensive and complex, requiring new ways to envision analyses. Using the Ray Surveyor software, we demonstrate that comparison of genomes based on their k-mer content allows reconstruction of phenetic trees without the need of prior data curation, such as core genome alignment of a species. We validated the methodology using simulated genomes and previously published phylogenomic studies of Streptococcus pneumoniae and Pseudomonas aeruginosa. We also investigated the relationship of specific genetic determinants with bacterial population structures. By comparing clusters from the complete genomic content of a genome population with clusters from specific functional categories of genes, we can determine how the population structures are correlated. Indeed, the strain clustering based on a subset of k-mers allows determination of its similarity with the whole genome clusters. We also applied this methodology on 42 species of bacteria to determine the correlational significance of five important bacterial genomic characteristics. For example, intrinsic resistance is more important in P. aeruginosa than in S. pneumoniae, and the former has increased correlation of its population structure with antibiotic resistance genes. The global view of the pangenome of bacteria also demonstrated the taxa-dependent interaction of population structure with antibiotic resistance, bacteriophage, plasmid, and mobile element k-mer data sets.201728957508
9004130.9992Shedding light on the bacterial resistance to toxic UV filters: a comparative genomic study. UV filters are toxic to marine bacteria that dominate the marine biomass. Ecotoxicology often studies the organism response but rarely integrates the toxicity mechanisms at the molecular level. In this study, in silico comparative genomics between UV filters sensitive and resistant bacteria were conducted in order to unravel the genes responsible for a resistance phenotype. The genomes of two environmentally relevant Bacteroidetes and three Firmicutes species were compared through pairwise comparison. Larger genomes were carried by bacteria exhibiting a resistant phenotype, favoring their ability to adapt to environmental stresses. While the antitoxin and CRISPR systems were the only distinctive features in resistant Bacteroidetes, Firmicutes displayed multiple unique genes that could support the difference between sensitive and resistant phenotypes. Several genes involved in ROS response, vitamin biosynthesis, xenobiotic degradation, multidrug resistance, and lipophilic compound permeability were shown to be exclusive to resistant species. Our investigation contributes to a better understanding of UV filters resistance phenotypes, by identifying pivotal genes involved in key pathways.202134760358
8388140.9992Essential genes from Arctic bacteria used to construct stable, temperature-sensitive bacterial vaccines. All bacteria share a set of evolutionarily conserved essential genes that encode products that are required for viability. The great diversity of environments that bacteria inhabit, including environments at extreme temperatures, place adaptive pressure on essential genes. We sought to use this evolutionary diversity of essential genes to engineer bacterial pathogens to be stably temperature-sensitive, and thus useful as live vaccines. We isolated essential genes from bacteria found in the Arctic and substituted them for their counterparts into pathogens of mammals. We found that substitution of nine different essential genes from psychrophilic (cold-loving) bacteria into mammalian pathogenic bacteria resulted in strains that died below their normal-temperature growth limits. Substitution of three different psychrophilic gene orthologs of ligA, which encode NAD-dependent DNA ligase, resulted in bacterial strains that died at 33, 35, and 37 degrees C. One ligA gene was shown to render Francisella tularensis, Salmonella enterica, and Mycobacterium smegmatis temperature-sensitive, demonstrating that this gene functions in both Gram-negative and Gram-positive lineage bacteria. Three temperature-sensitive F. tularensis strains were shown to induce protective immunity after vaccination at a cool body site. About half of the genes that could be tested were unable to mutate to temperature-resistant forms at detectable levels. These results show that psychrophilic essential genes can be used to create a unique class of bacterial temperature-sensitive vaccines for important human pathogens, such as S. enterica and Mycobacterium tuberculosis.201020624965
8711150.9992Novel soil bacteria possess diverse genes for secondary metabolite biosynthesis. In soil ecosystems, microorganisms produce diverse secondary metabolites such as antibiotics, antifungals and siderophores that mediate communication, competition and interactions with other organisms and the environment(1,2). Most known antibiotics are derived from a few culturable microbial taxa (3) , and the biosynthetic potential of the vast majority of bacteria in soil has rarely been investigated (4) . Here we reconstruct hundreds of near-complete genomes from grassland soil metagenomes and identify microorganisms from previously understudied phyla that encode diverse polyketide and nonribosomal peptide biosynthetic gene clusters that are divergent from well-studied clusters. These biosynthetic loci are encoded by newly identified members of the Acidobacteria, Verrucomicobia and Gemmatimonadetes, and the candidate phylum Rokubacteria. Bacteria from these groups are highly abundant in soils(5-7), but have not previously been genomically linked to secondary metabolite production with confidence. In particular, large numbers of biosynthetic genes were characterized in newly identified members of the Acidobacteria, which is the most abundant bacterial phylum across soil biomes (5) . We identify two acidobacterial genomes from divergent lineages, each of which encodes an unusually large repertoire of biosynthetic genes with up to fifteen large polyketide and nonribosomal peptide biosynthetic loci per genome. To track gene expression of genes encoding polyketide synthases and nonribosomal peptide synthetases in the soil ecosystem that we studied, we sampled 120 time points in a microcosm manipulation experiment and, using metatranscriptomics, found that gene clusters were differentially co-expressed in response to environmental perturbations. Transcriptional co-expression networks for specific organisms associated biosynthetic genes with two-component systems, transcriptional activation, putative antimicrobial resistance and iron regulation, linking metabolite biosynthesis to processes of environmental sensing and ecological competition. We conclude that the biosynthetic potential of abundant and phylogenetically diverse soil microorganisms has previously been underestimated. These organisms may represent a source of natural products that can address needs for new antibiotics and other pharmaceutical compounds.201829899444
8392160.9992Identification of variable genomic regions related to stress response in Oenococcus oeni. The lactic acid bacterium Oenococcus oeni is the most important species involved in malolactic fermentation due to its capability to survive in presence of ethanol and in the acidic environment of wine. In order to identify novel genes involved in adaptation to wine, a new approach using genome-wide analysis based on stress-related genes was performed in strain O. oeni PSU-1, and 106 annotated stress genes were identified. The in silico analysis revealed the high similarity of all those genes through 57 O. oeni genomes; however, seven variable regions of genomic plasticity could be determined for their different presence observed among these strains. Regions 3 and 5 had the typical hallmarks of horizontal transfer, suggesting that the strategy of acquiring genes from other bacteria enhanced the fitness of O. oeni strains. Certain genes related to stress resistance were described in these regions, and similarities of putative acquired regions with other lactic acid bacteria species were found. Some genomic fragments present in all the strains were described and another new genomic island harbouring a threonine dehydrogenase was found. The association of selected sequences with adaptation to wine was assessed by screening 31 O. oeni strains using PCR of single genes, but no sequences were found to be exclusive to highly performing malolactic fermentation strains. This study provides new information about the genomic variability of O. oeni strains contributing to a further understanding of this species and the relationship of its genomic traits with the ability to adapt to stress conditions.201729195994
4382170.9992A bioinformatic approach to understanding antibiotic resistance in intracellular bacteria through whole genome analysis. Intracellular bacteria survive within eukaryotic host cells and are difficult to kill with certain antibiotics. As a result, antibiotic resistance in intracellular bacteria is becoming commonplace in healthcare institutions. Owing to the lack of methods available for transforming these bacteria, we evaluated the mechanisms of resistance using molecular methods and in silico genome analysis. The objective of this review was to understand the molecular mechanisms of antibiotic resistance through in silico comparisons of the genomes of obligate and facultative intracellular bacteria. The available data on in vitro mutants reported for intracellular bacteria were also reviewed. These genomic data were analysed to find natural mutations in known target genes involved in antibiotic resistance and to look for the presence or absence of different resistance determinants. Our analysis revealed the presence of tetracycline resistance protein (Tet) in Bartonella quintana, Francisella tularensis and Brucella ovis; moreover, most of the Francisella strains possessed the blaA gene, AmpG protein and metallo-beta-lactamase family protein. The presence or absence of folP (dihydropteroate synthase) and folA (dihydrofolate reductase) genes in the genome could explain natural resistance to co-trimoxazole. Finally, multiple genes encoding different efflux pumps were studied. This in silico approach was an effective method for understanding the mechanisms of antibiotic resistance in intracellular bacteria. The whole genome sequence analysis will help to predict several important phenotypic characteristics, in particular resistance to different antibiotics. In the future, stable mutants should be obtained through transformation methods in order to demonstrate experimentally the determinants of resistance in intracellular bacteria.200818619818
3809180.9991High abundance of virulence gene homologues in marine bacteria. Marine bacteria can cause harm to single-celled and multicellular eukaryotes. However, relatively little is known about the underlying genetic basis for marine bacterial interactions with higher organisms. We examined whole-genome sequences from a large number of marine bacteria for the prevalence of homologues to virulence genes and pathogenicity islands known from bacteria that are pathogenic to terrestrial animals and plants. As many as 60 out of 119 genomes of marine bacteria, with no known association to infectious disease, harboured genes of virulence-associated types III, IV, V and VI protein secretion systems. Type III secretion was relatively uncommon, while type IV was widespread among alphaproteobacteria (particularly among roseobacters) and type VI was primarily found among gammaproteobacteria. Other examples included homologues of the Yersinia murine toxin and a phage-related 'antifeeding' island. Analysis of the Global Ocean Sampling metagenomic data indicated that virulence genes were present in up to 8% of the planktonic bacteria, with highest values in productive waters. From a marine ecology perspective, expression of these widely distributed genes would indicate that some bacteria infect or even consume live cells, that is, generate a previously unrecognized flow of organic matter and nutrients directly from eukaryotes to bacteria.200919207573
8379190.9991Comparative study of the marR genes within the family Enterobacteriaceae. marR genes are members of an ancient family originally identified in Escherichia coli. This family is widely distributed in archaea and bacteria. Homologues of this family have a conserved winged helix fold. MarR proteins are involved in non-specific resistance systems conferring resistance to multiple antibiotics. Extensive studies have shown the importance of MarR proteins in physiology and pathogenicity in Enterobacteria, but little is known about their origin or evolution. In this study, all the marR genes in 43 enterobacterial genomes representing 14 genera were identified, and the phylogenetic relationships and genetic parameters were analyzed. Several major findings were made. Three conserved marR genes originated earlier than Enterobacteriaceae and a geneloss event was found to have taken place in Yersinia pestis Antiqua. Three functional genes, rovA, hor, and slyA, were found to be clear orthologs among Enterobacteriaceae. The copy number of marR genes in Enterobacteriaceae was found to vary from 2 to 11. These marR genes exhibited a faster rate of nucleotide substitution than housekeeping genes did. Specifically, the regions of marR domain were found to be subject to strong purifying selection. The phylogenetic relationship and genetic parameter analyses were consistent with conservation and specificity of marR genes. These dual characters helped MarR to maintain a conserved binding motif and variable C-terminus, which are important to adaptive responses to a number of external stimuli in Enterobacteriaceae.201424723108