RESUMO
Chromatin regulates the selectivity of retroviral integration into the genome of infected cells. At the nucleosome level, both histones and DNA structure are involved in this regulation. We propose a strategy that allows to specifically study a single factor: the DNA distortion induced by the nucleosome. This strategy relies on mimicking this distortion using DNA minicircles (MCs) having a fixed rotational orientation of DNA curvature, coupled with atomic-resolution modeling. Contrasting MCs with linear DNA fragments having identical sequences enabled us to analyze the impact of DNA distortion on the efficiency and selectivity of integration. We observed a global enhancement of HIV-1 integration in MCs and an enrichment of integration sites in the outward-facing DNA major grooves. Both of these changes are favored by LEDGF/p75, revealing a new, histone-independent role of this integration cofactor. PFV integration is also enhanced in MCs, but is not associated with a periodic redistribution of integration sites, thus highlighting its distinct catalytic properties. MCs help to separate the roles of target DNA structure, histone modifications and integrase (IN) cofactors during retroviral integration and to reveal IN-specific regulation mechanisms.
Assuntos
DNA Circular/química , DNA Viral/química , Conformação de Ácido Nucleico , Retroviridae/fisiologia , Integração Viral , Biblioteca Gênica , Integrase de HIV/metabolismo , HIV-1/fisiologia , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Modelos Moleculares , Nucleossomos/metabolismoRESUMO
Six Gram-negative, non-motile, non-spore-forming, non-pigmented, oxidase- and catalase-positive bacterial strains were deposited in 1972, in the Collection of the Institut Pasteur (CIP), Paris, France. The strains, previously identified as members of the genus Moraxella on the basis of their phenotypic and biochemical characteristics, were placed within the genus Psychrobacter based on the results from comparative 16S rRNA gene sequence studies. Their closest phylogenetic relatives were Psychrobacter sanguinis CIP 110993T, Psychrobacter phenylpyruvicus CIP 82.27T and Psychrobacter lutiphocae CIP 110018T. The DNA G+C contents were between 42.1 and 42.7 mol%. The predominant fatty acids were C18â:â1ω9c, C16â:â0, C12â:â0 3-OH, and C18â:â0. Average nucleotide identity between the six strains and their closest phylogenetic relatives, as well as their phenotypic characteristics, supported the assignment of these strains to two novel species within the genus Psychrobacter. The proposed names for these strains are Psychrobacter pasteurii sp. nov., for which the type strain is A1019T (=CIP 110853T=CECT 9184T), and Psychrobacter piechaudii sp. nov., for which the type strain is 1232T (=CIP110854T=CECT 9185T).
Assuntos
Filogenia , Psychrobacter/classificação , Técnicas de Tipagem Bacteriana , Composição de Bases , DNA Bacteriano/genética , DNA Ribossômico/genética , Ácidos Graxos/química , França , Psychrobacter/genética , Psychrobacter/isolamento & purificação , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
MicroScope is an integrated platform dedicated to both the methodical updating of microbial genome annotation and to comparative analysis. The resource provides data from completed and ongoing genome projects (automatic and expert annotations), together with data sources from post-genomic experiments (i.e. transcriptomics, mutant collections) allowing users to perfect and improve the understanding of gene functions. MicroScope (http://www.genoscope.cns.fr/agc/microscope) combines tools and graphical interfaces to analyse genomes and to perform the manual curation of gene annotations in a comparative context. Since its first publication in January 2006, the system (previously named MaGe for Magnifying Genomes) has been continuously extended both in terms of data content and analysis tools. The last update of MicroScope was published in 2009 in the Database journal. Today, the resource contains data for >1600 microbial genomes, of which â¼300 are manually curated and maintained by biologists (1200 personal accounts today). Expert annotations are continuously gathered in the MicroScope database (â¼50 000 a year), contributing to the improvement of the quality of microbial genomes annotations. Improved data browsing and searching tools have been added, original tools useful in the context of expert annotation have been developed and integrated and the website has been significantly redesigned to be more user-friendly. Furthermore, in the context of the European project Microme (Framework Program 7 Collaborative Project), MicroScope is becoming a resource providing for the curation and analysis of both genomic and metabolic data. An increasing number of projects are related to the study of environmental bacterial (meta)genomes that are able to metabolize a large variety of chemical compounds that may be of high industrial interest.
Assuntos
Bactérias/genética , Bactérias/metabolismo , Bases de Dados Genéticas , Genoma Bacteriano , Enzimas/genética , Evolução Molecular , Perfilação da Expressão Gênica , Genoma Arqueal , Genômica , Internet , Redes e Vias Metabólicas/genética , Software , Sintenia , Integração de SistemasRESUMO
We present the complete genome sequence of Bradyrhizobium sp. 62B, a strain isolated from the root nodules of peanut plants that grow in central Argentina. The genome consists of 8.15 Mbp, distributed into a chromosome of 7.29 Mbp and a plasmid of 0.86 Mbp.
RESUMO
BACKGROUND: Mesorhizobium metallidurans STM 2683T and Mesorhizobium sp. strain STM 4661 were isolated from nodules of the metallicolous legume Anthyllis vulneraria from distant mining spoils. They tolerate unusually high Zinc and Cadmium concentrations as compared to other mesorhizobia. This work aims to study the gene expression profiles associated with Zinc or Cadmium exposure and to identify genes involved in metal tolerance in these two metallicolous Mesorhizobium strains of interest for mine phytostabilization purposes. RESULTS: The draft genomes of the two Mezorhizobium strains were sequenced and used to map RNAseq data obtained after Zinc or Cadmium stresses. Comparative genomics and transcriptomics allowed the rapid discovery of metal-specific or/and strain-specific genes. Respectively 1.05% (72/6,844) and 0.97% (68/6,994) predicted Coding DNA Sequences (CDS) for STM 2683 and STM 4661 were significantly differentially expressed upon metal exposure. Among these, a significant number of CDS involved in transport (13/72 and 13/68 for STM 2683 and STM 4661, respectively) and sequestration (15/72 and 16/68 for STM 2683 and STM 4661, respectively) were identified. Thirteen CDS presented homologs in both strains and were differentially regulated by Zinc and/or Cadmium. For instance, several PIB-type ATPases and genes likely to participate in metal sequestration were identified. Among the conserved CDS that showed differential regulation in the two isolates, we also found znuABC homologs encoding for a high affinity ABC-type Zinc import system probably involved in Zinc homeostasis. Additionally, global analyses suggested that both metals also repressed significantly the translational machinery. CONCLUSIONS: The comparative RNAseq-based approach revealed a relatively low number of genes significantly regulated in the two Mesorhizobium strains. Very few of them were involved in the non-specific metal response, indicating that the approach was well suited for identifying genes that specifically respond to Zinc and Cadmium. Among significantly up-regulated genes, several encode metal efflux and sequestration systems which can be considered as the most widely represented mechanisms of rhizobial metal tolerance. Downstream functional studies will increase successful phytostabilization strategies by selecting appropriate metallicolous rhizobial partners.
Assuntos
Cádmio/farmacologia , Genômica , Mesorhizobium/efeitos dos fármacos , Mesorhizobium/genética , Simbiose , Transcrição Gênica/efeitos dos fármacos , Zinco/farmacologia , Transportadores de Cassetes de Ligação de ATP/metabolismo , Adenosina Trifosfatases/metabolismo , Antibacterianos/metabolismo , Transporte Biológico/efeitos dos fármacos , Transporte Biológico/genética , Mapeamento Cromossômico , Sequência Conservada , Genes Bacterianos/genética , Mesorhizobium/metabolismo , Mesorhizobium/fisiologia , Anotação de Sequência Molecular , Análise de Sequência de RNA , Especificidade da Espécie , Transcriptoma/efeitos dos fármacosRESUMO
Continuous updating of the genome sequence of Bacillus subtilis, the model of the Firmicutes, is a basic requirement needed by the biology community. In this work new genomic objects have been included (toxin/antitoxin genes and small RNA genes) and the metabolic network has been entirely updated. The curated view of the validated metabolic pathways present in the organism as of 2012 shows several significant differences from pathways present in the other bacterial reference, Escherichia coli: variants in synthesis of cofactors (thiamine, biotin, bacillithiol), amino acids (lysine, methionine), branched-chain fatty acids, tRNA modification and RNA degradation. In this new version, gene products that are enzymes or transporters are explicitly linked to the biochemical reactions of the RHEA reaction resource (http://www.ebi.ac.uk/rhea/), while novel compound entries have been created in the database Chemical Entities of Biological Interest (http://www.ebi.ac.uk/chebi/). The newly annotated sequence is deposited at the International Nucleotide Sequence Data Collaboration with accession number AL009126.4.
Assuntos
Bacillus subtilis/metabolismo , Proteínas de Bactérias/metabolismo , Genoma Bacteriano , Redes e Vias Metabólicas/genética , Bacillus subtilis/genética , Proteínas de Bactérias/genética , Genômica , Anotação de Sequência Molecular , Dados de Sequência Molecular , Análise de Sequência de DNARESUMO
It is unclear how gene order within the chromosome influences genome evolution. Bacteria cluster transcription and translation genes close to the replication origin (oriC). In Vibrio cholerae, relocation of s10-spc-α locus (S10), the major locus of ribosomal protein genes, to ectopic genomic positions shows that its relative distance to the oriC correlates to a reduction in growth rate, fitness, and infectivity. To test the long-term impact of this trait, we evolved 12 populations of V. cholerae strains bearing S10 at an oriC-proximal or an oriC-distal location for 1,000 generations. During the first 250 generations, positive selection was the main force driving mutation. After 1,000 generations, we observed more nonadaptative mutations and hypermutator genotypes. Populations fixed inactivating mutations at many genes linked to virulence: flagellum, chemotaxis, biofilm, and quorum sensing. Throughout the experiment, all populations increased their growth rates. However, those bearing S10 close to oriC remained the fittest, indicating that suppressor mutations cannot compensate for the genomic position of the main ribosomal protein locus. Selection and sequencing of the fastest-growing clones allowed us to characterize mutations inactivating, among other sites, flagellum master regulators. Reintroduction of these mutations into the wild-type context led to a ≈10% growth improvement. In conclusion, the genomic location of ribosomal protein genes conditions the evolutionary trajectory of V. cholerae. While genomic content is highly plastic in prokaryotes, gene order is an underestimated factor that conditions cellular physiology and evolution. A lack of suppression enables artificial gene relocation as a tool for genetic circuit reprogramming. IMPORTANCE The bacterial chromosome harbors several entangled processes such as replication, transcription, DNA repair, and segregation. Replication begins bidirectionally at the replication origin (oriC) until the terminal region (ter) organizing the genome along the ori-ter axis gene order along this axis could link genome structure to cell physiology. Fast-growing bacteria cluster translation genes near oriC. In Vibrio cholerae, moving them away was feasible but at the cost of losing fitness and infectivity. Here, we evolved strains harboring ribosomal genes close or far from oriC. Growth rate differences persisted after 1,000 generations. No mutation was able to compensate for the growth defect, showing that ribosomal gene location conditions their evolutionary trajectory. Despite the high plasticity of bacterial genomes, evolution has sculpted gene order to optimize the ecological strategy of the microorganism. We observed growth rate improvement throughout the evolution experiment that occurred at expense of energetically costly processes such the flagellum biosynthesis and virulence-related functions. From the biotechnological point of view, manipulation of gene order enables altering bacterial growth with no escape events.
Assuntos
Vibrio cholerae , Vibrio cholerae/genética , Proteínas Ribossômicas/genética , Genoma Bacteriano , Mutação , Cromossomos , Proteínas de Bactérias/genéticaRESUMO
We report the complete genome sequence of Burkholderia ambifaria strain Q53, an environmental rhizobacterium isolated from the rhizosphere of peanut plants. The genome consists of 7.4 Mbp distributed into three circular chromosomes and was determined using a hybrid long- and short-read assembly approach.
RESUMO
Here, we report the complete genome sequence of Mesorhizobium mediterraneum R31, a rhizobial strain recommended and used as a commercial inoculant for chickpea in Argentina. The genome consists of 7.25 Mb, distributed into four circular replicons: a chromosome of 6.72 Mbp and three plasmids of 0.29, 0.17, and 0.07 Mbp.
RESUMO
Entamoeba is a genus of Amoebozoa that includes the intestine-colonizing pathogenic species Entamoeba histolytica. To understand the basis of gene regulation in E. histolytica from an evolutionary perspective, we have profiled the transcriptomes of its closely related species E. dispar, E. moshkovskii and E. invadens. Genome-wide identification of transcription start sites (TSS) and polyadenylation sites (PAS) revealed the similarities and differences of their gene regulatory sequences. In particular, we found the widespread initiation of antisense transcription from within the gene coding sequences is a common feature among all Entamoeba species. Interestingly, we observed the enrichment of antisense transcription in genes involved in several processes that are common to species infecting the human intestine, e.g., the metabolism of phospholipids. These results suggest a potentially conserved and compact gene regulatory system in Entamoeba.
RESUMO
We report the complete genome sequence of Mesorhizobium ciceri strain R30, a rhizobium strain recommended and used as a commercial inoculant for chickpea in Argentina. The genome consists of almost 7 Mb, distributed into two circular replicons: a chromosome of 6.49 Mb and a plasmid of 0.46 Mb.
RESUMO
We present the complete genome sequence of Bradyrhizobium sp. strain C-145, one of the most widely used nitrogen-fixing rhizobacteria for inoculating peanut crops in Argentina. The genome consists of 9.53 Mbp in a single circular chromosome and was determined using a hybrid long- and short-read assembly approach.
RESUMO
Escherichia coli exhibits a wide range of lifestyles encompassing commensalism and various pathogenic behaviors which its highly dynamic genome contributes to develop. How environmental and host factors shape the genetic structure of E. coli strains remains, however, largely unknown. Following a previous study of E. coli genomic diversity, we investigated its diversity at the metabolic level by building and analyzing the genome-scale metabolic networks of 29 E. coli strains (8 commensal and 21 pathogenic strains, including 6 Shigella strains). Using a tailor-made reconstruction strategy, we significantly improved the completeness and accuracy of the metabolic networks over default automatic reconstruction processes. Among the 1,545 reactions forming E. coli panmetabolism, 885 reactions were common to all strains. This high proportion of core reactions (57%) was found to be in sharp contrast to the low proportion (13%) of core genes in the E. coli pangenome, suggesting less diversity of metabolic functions compared to that of all gene functions. Core reactions were significantly overrepresented among biosynthetic reactions compared to the more variable degradation processes. Differences between metabolic networks were found to follow E. coli phylogeny rather than pathogenic phenotypes, except for Shigella networks, which were significantly more distant from the others. This suggests that most metabolic changes in non-Shigella strains were not driven by their pathogenic phenotypes. Using a supervised method, we were yet able to identify small sets of reactions related to pathogenicity or commensalism. The quality of our reconstructed networks also makes them reliable bases for building metabolic models.
Assuntos
Escherichia coli/genética , Escherichia coli/metabolismo , Genoma Bacteriano , Redes e Vias Metabólicas/genética , Biologia Computacional , Variação GenéticaRESUMO
BACKGROUND: The Ralstonia solanacearum species complex includes thousands of strains pathogenic to an unusually wide range of plant species. These globally dispersed and heterogeneous strains cause bacterial wilt diseases, which have major socio-economic impacts. Pathogenicity is an ancestral trait in R. solanacearum and strains with high genetic variation can be subdivided into four phylotypes, correlating to isolates from Asia (phylotype I), the Americas (phylotype IIA and IIB), Africa (phylotype III) and Indonesia (phylotype IV). Comparison of genome sequences strains representative of this phylogenetic diversity can help determine which traits allow this bacterium to be such a pathogen of so many different plant species and how the bacteria survive in many different habitats. RESULTS: The genomes of three tomato bacterial wilt pathogens, CFBP2957 (phy. IIA), CMR15 (phy. III) and PSI07 (phy. IV) were sequenced and manually annotated. These genomes were compared with those of three previously sequenced R. solanacearum strains: GMI1000 (tomato, phy. I), IPO1609 (potato, phy. IIB), and Molk2 (banana, phy. IIB). The major genomic features (size, G+C content, number of genes) were conserved across all of the six sequenced strains. Despite relatively high genetic distances (calculated from average nucleotide identity) and many genomic rearrangements, more than 60% of the genes of the megaplasmid and 70% of those on the chromosome are syntenic. The three new genomic sequences revealed the presence of several previously unknown traits, probably acquired by horizontal transfers, within the genomes of R. solanacearum, including a type IV secretion system, a rhi-type anti-mitotic toxin and two small plasmids. Genes involved in virulence appear to be evolving at a faster rate than the genome as a whole. CONCLUSIONS: Comparative analysis of genome sequences and gene content confirmed the differentiation of R. solanacearum species complex strains into four phylotypes. Genetic distances between strains, in conjunction with CGH analysis of a larger set of strains, revealed differences great enough to consider reclassification of the R. solanacearum species complex into three species. The data are still too fragmentary to link genomic classification and phenotypes, but these new genome sequences identify a pan-genome more representative of the diversity in the R. solanancearum species complex.
Assuntos
Evolução Molecular , Variação Genética , Genoma Bacteriano/genética , Ralstonia solanacearum/genética , Solanum lycopersicum/microbiologia , Hibridização Genômica Comparativa , Sequência Conservada , Genes Bacterianos/genética , Ilhas Genômicas/genética , Análise de Sequência com Séries de Oligonucleotídeos , Filogenia , Plasmídeos/genética , Ralstonia solanacearum/metabolismo , Fatores de Virulência/genéticaRESUMO
Natural antisense transcripts (NAT) have been reported in prokaryotes and eukaryotes. While the functions of most reported NATs remain unknown, their potentials in regulating the transcription of their counterparts have been speculated. Entamoeba histolytica, which is a unicellular eukaryotic parasite, has a compact protein-coding genome with very short intronic and intergenic regions. The regulatory mechanisms of gene expression in this compact genome are under-described. In this study, by genome-wide mapping of RNA-Seq data in the genome of E. histolytica, we show that a substantial fraction of its protein-coding genes (28%) has significant transcription on their opposite strand (i.e. NAT). Intriguingly, we found the location of transcription start sites or polyadenylation sites of NAT are determined by the specific motifs encoded on the opposite strand of the gene coding sequences, thereby providing a compact regulatory system for gene transcription. Moreover, we demonstrated that NATs are globally up-regulated under various environmental conditions including temperature stress and pathogenicity. While NATs do not appear to be consequences of spurious transcription, they may play a role in regulating gene expression in E. histolytica, a hypothesis which needs to be tested.
Assuntos
Entamoeba histolytica/genética , RNA Antissenso/genética , Transcrição Gênica , Entamoeba histolytica/metabolismo , Perfilação da Expressão Gênica , RNA Antissenso/metabolismoRESUMO
Several phenanthrolinic analogs of quinolones have been synthesized and their antibacterial activity tested against Mycobacterium tuberculosis, other mycobacterial species and bacteria from other genera. Some of them show high activity (of the range observed for rifampicin) against M. tuberculosis replicating in vitro and in vivo (infected macrophages) conditions. These derivatives show the same activity with all or several M. tuberculosis complex bacterial mutants resistant to fluoroquinolones (FQ). This opens the way to the construction of new drugs for the treatment of FQ resistant bacterial infections, including tuberculosis. Several compounds showed also activity against Staphylococcus aureus and probably other species. These compounds do not show major toxicity. We conclude that the novel phenanthrolinic derivatives described here are potent hits for further developments of new antibiotics against bacterial infectious diseases including tuberculosis in particular those resistant to FQ.
Assuntos
Antituberculosos/química , Antituberculosos/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , Fenantrolinas/química , Quinolonas/química , Quinolonas/farmacologia , Desenho de Fármacos , Farmacorresistência Bacteriana/efeitos dos fármacos , Testes de Sensibilidade MicrobianaRESUMO
Transcription factor networks, together with histone modifications and signalling pathways, underlie the establishment and maintenance of gene regulatory architectures associated with the molecular identity of each cell type. However, how master transcription factors individually impact the epigenomic landscape and orchestrate the behaviour of regulatory networks under different environmental constraints is only partially understood. Here, we show that the transcription factor Nanog deploys multiple distinct mechanisms to enhance embryonic stem cell self-renewal. In the presence of LIF, which fosters self-renewal, Nanog rewires the pluripotency network by promoting chromatin accessibility and binding of other pluripotency factors to thousands of enhancers. In the absence of LIF, Nanog blocks differentiation by sustaining H3K27me3, a repressive histone mark, at developmental regulators. Among those, we show that the repression of Otx2 plays a preponderant role. Our results underscore the versatility of master transcription factors, such as Nanog, to globally influence gene regulation during developmental processes.
Assuntos
Autorrenovação Celular/fisiologia , Células-Tronco Embrionárias Murinas/citologia , Células-Tronco Embrionárias Murinas/metabolismo , Proteína Homeobox Nanog/metabolismo , Animais , Linhagem Celular , Autorrenovação Celular/genética , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica , Redes Reguladoras de Genes , Código das Histonas/genética , Fator Inibidor de Leucemia/genética , Fator Inibidor de Leucemia/metabolismo , Camundongos , Proteína Homeobox Nanog/genética , Fatores de Transcrição Otx/genética , Fatores de Transcrição Otx/metabolismoRESUMO
Horizontal gene transfer (HGT) is considered as a major source of innovation in bacteria, and as such is expected to drive adaptation to new ecological niches. However, among the many genes acquired through HGT along the diversification history of genomes, only a fraction may have actively contributed to sustained ecological adaptation. We used a phylogenetic approach accounting for the transfer of genes (or groups of genes) to estimate the history of genomes in Agrobacterium biovar 1, a diverse group of soil and plant-dwelling bacterial species. We identified clade-specific blocks of cotransferred genes encoding coherent biochemical pathways that may have contributed to the evolutionary success of key Agrobacterium clades. This pattern of gene coevolution rejects a neutral model of transfer, in which neighboring genes would be transferred independently of their function and rather suggests purifying selection on collectively coded acquired pathways. The acquisition of these synapomorphic blocks of cofunctioning genes probably drove the ecological diversification of Agrobacterium and defined features of ancestral ecological niches, which consistently hint at a strong selective role of host plant rhizospheres.
Assuntos
Agrobacterium/citologia , Agrobacterium/genética , Evolução Biológica , Ecologia , Variação Genética , Genoma Bacteriano , Biologia Computacional , Sequenciamento de Nucleotídeos em Larga Escala , Filogenia , SoftwareRESUMO
Rhizobium mesoamericanum STM3625 is a Mimosa pudica symbiont isolated in French Guiana. This strain serves as a model bacterium for comparison of adaptation to mutualism (symbiotic traits, bacterial genetic programs for plant infection) between alpha and beta rhizobial symbionts of Mimosa pudica.
RESUMO
Tropical aquatic species of the legume genus Aeschynomene are stem- and root-nodulated by bradyrhizobia strains that exhibit atypical features such as photosynthetic capacities or the use of a nod gene-dependent (ND) or a nod gene-independent (NI) pathway to enter into symbiosis with legumes. In this study we used a comparative genomics approach on nine Aeschynomene symbionts representative of their phylogenetic diversity. We produced draft genomes of bradyrhizobial strains representing different phenotypes: five NI photosynthetic strains (STM3809, ORS375, STM3847, STM4509 and STM4523) in addition to the previously sequenced ORS278 and BTAi1 genomes, one photosynthetic strain ORS285 hosting both ND and NI symbiotic systems, and one NI non-photosynthetic strain (STM3843). Comparative genomics allowed us to infer the core, pan and dispensable genomes of Aeschynomene bradyrhizobia, and to detect specific genes and their location in Genomic Islands (GI). Specific gene sets linked to photosynthetic and NI/ND abilities were identified, and are currently being studied in functional analyses.