Suchergebnisse

The halophilic bacterium Salinibacter ruber is an abundant and ecologically important member of halophilic communities worldwide. Given its broad distribution and high intraspecific genetic diversity, S. ruber is considered one of the main models for ecological and evolutionary studies of bacterial adaptation to hypersaline environments. However, current insights on the genomic diversity of this species is limited to the comparison of the genomes of two co-isolated strains. Here, we present a comparative genomic analysis of eight S. ruber strains isolated at two different time points in each of two different Mediterranean solar salterns. Our results show an open pangenome with contrasting evolutionary patterns in the core and accessory genomes. We found that the core genome is shaped by extensive homologous recombination (HR), which results in limited sequence variation within population clusters. In contrast, the accessory genome is modulated by horizontal gene transfer (HGT), with genomic islands and plasmids acting as gateways to the rest of the genome. In addition, both types of genetic exchange are modulated by restriction and modification (RM) or CRISPR-Cas systems. Finally, genes differentially impacted by such processes reveal functional processes potentially relevant for environmental interactions and adaptation to extremophilic conditions. Altogether, our results support scenarios that conciliate "Neutral" and "Constant Diversity" models of bacterial evolution. ; PG-T was an FPI-MINECO fellow. TG group acknowledges support of the Spanish Ministry of Economy and Competitiveness grants, 'Centro de Excelencia Severo Ochoa 2013–2017' SEV-2012-0208, and BFU2015-67107 cofounded by European Regional Development Fund (ERDF); from the CERCA Program/Generalitat de Catalunya; from the Catalan Research Agency (AGAUR) SGR857, and grant from the European Union's Horizon 2020 Research and Innovation Program under the grant agreement ERC-2016-724173 the Marie Sklodowska-Curie grant agreement No. H2020-MSCA-ITN-2014-642095. We acknowledge the support of the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) to the EMBL partnership.

Homologous recombination (HR) enables the exchange of genetic material between and within species. Recent studies suggest that this process plays a major role in the microevolution of microbial genomes, contributing to core genome homogenization and to the maintenance of cohesive population structures. However, we still have a very poor understanding of the possible adaptive roles of intraspecific HR and of the factors that determine its differential impact across clades and lifestyles. Here we used a unified methodological framework to assess HR in 338 complete genomes from 54 phylogenetically diverse and representative prokaryotic species, encompassing different lifestyles and a broad phylogenetic distribution. Our results indicate that lifestyle and presence of restriction-modification (RM) machineries are among the main factors shaping HR patterns, with symbionts and intracellular pathogens having the lowest HR levels. Similarly, the size of exchanged genomic fragments correlated with the presence of RM and competence machineries. Finally, genes exchanged by HR showed functional enrichments which could be related to adaptations to different environments and ecological strategies. Taken together, our results clarify the factors underlying HR impact and suggest important adaptive roles of genes exchanged through this mechanism. Our results also revealed that the extent of genetic exchange correlated with lifestyle and some genomic features. Moreover, the genes in exchanged regions were enriched for functions that reflected specific adaptations, supporting identification of HR as one of the main evolutionary mechanisms shaping prokaryotic core genomes. ; The group of J.A. is funded by grant CLG2015_66686-C3-03 from the Spanish Ministry of Economy and Competitiveness (MINECO), which is cofinanced with FEDER support from the European Union. P.G.-T. was an FPI-MINECO fellow associated with project CGL2012-39627-C03-01 (to J.A.). The T.G. group acknowledges support from the Spanish Ministry of Economy and Competitiveness (grants "Centro de Excelencia Severo Ochoa 2013-2017" SEV-2012-0208 and BFU2015-67107; cofounded by European Regional Development Fund [ERDF]); from the CERCA Program/Generalitat de Catalunya; from the Catalan Research Agency (AGAUR) (grant SGR857); and from the European Union's Horizon 2020 research and innovation program under grant agreement ERC-2016-724173 (Marie Sklodowska-Curie grant agreement no. H2020-MSCA-ITN-2014-642095).

Homologous recombination (HR) enables the exchange of genetic material between and within species. Recent studies suggest that this process plays a major role in the microevolution of microbial genomes, contributing to core genome homogenization and to the maintenance of cohesive population structures. However, we still have a very poor understanding of the possible adaptive roles of intraspecific HR and of the factors that determine its differential impact across clades and lifestyles. Here we used a unified methodological framework to assess HR in 338 complete genomes from 54 phylogenetically diverse and representative prokaryotic species, encompassing different lifestyles and a broad phylogenetic distribution. Our results indicate that lifestyle and presence of restriction-modification (RM) machineries are among the main factors shaping HR patterns, with symbionts and intracellular pathogens having the lowest HR levels. Similarly, the size of exchanged genomic fragments correlated with the presence of RM and competence machineries. Finally, genes exchanged by HR showed functional enrichments which could be related to adaptations to different environments and ecological strategies. Taken together, our results clarify the factors underlying HR impact and suggest important adaptive roles of genes exchanged through this mechanism. Our results also revealed that the extent of genetic exchange correlated with lifestyle and some genomic features. Moreover, the genes in exchanged regions were enriched for functions that reflected specific adaptations, supporting identification of HR as one of the main evolutionary mechanisms shaping prokaryotic core genomes.IMPORTANCE Microbial populations exchange genetic material through a process called homologous recombination. Although this process has been studied in particular organisms, we lack an understanding of its differential impact over the genome and across microbes with different life-styles. We used a common analytical framework to assess this process in a representative set of microorganisms. Our results uncovered important trends. First, microbes with different lifestyles are differentially impacted, with endosymbionts and obligate pathogens being those less prone to undergo this process. Second, certain genetic elements such as restriction-modification systems seem to be associated with higher rates of recombination. Most importantly, recombined genomes show the footprints of natural selection in which recombined regions preferentially contain genes that can be related to specific ecological adaptations. Taken together, our results clarify the relative contributions of factors modulating homologous recombination and show evidence for a clear a role of this process in shaping microbial genomes and driving ecological adaptations. ; The group of J.A. is funded by grant CLG2015_66686-C3-03 from the Spanish Ministry of Economy and Competitiveness (MINECO), which is cofinanced with FEDER support from the European Union. P.G.-T. was an FPI-MINECO fellow associated with project CGL2012-39627-C03-01 (to J.A.). The T.G. group acknowledges support from the Spanish Ministry of Economy and Competitiveness (grants "Centro de Excelencia Severo Ochoa 2013-2017" SEV-2012-0208 and BFU2015-67107; cofounded by European Regional Development Fund [ERDF]); from the CERCA Program/Generalitat de Catalunya; from the Catalan Research Agency (AGAUR) (grant SGR857); and from the European Union's Horizon 2020 research and innovation program under grant agreement ERC-2016-724173 (Marie Sklodowska-Curie grant agreement no. H2020-MSCA-ITN-2014-642095).

Comparative genomics, metagenomics, and single-cell technologies have shown that populations of microbial species encompass assemblages of closely related strains. This raises the question of whether individual bacterial lineages respond to the presence of their close relatives by modifying their gene expression or, instead, whether assemblages simply act as the arithmetic addition of their individual components. Here, we took advantage of transcriptome sequencing to address this question. For this, we analyzed the transcriptomes of two closely related strains of the extremely halophilic bacterium Salinibacter ruber grown axenically and in coculture. These organisms dominate bacterial assemblages in hypersaline environments worldwide. The strains used here cooccurred in the natural environment and are 100% identical in their 16S rRNA genes, and each strain harbors an accessory genome representing 10% of its complete genome. Overall, transcriptomic patterns from pure cultures were very similar for both strains. Expression was detected along practically the whole genome albeit with some genes at low levels. A subset of genes was very highly expressed in both strains, including genes coding for the light-driven proton pump xanthorhodopsin, genes involved in the stress response, and genes coding for transcriptional regulators. Expression differences between pure cultures affected mainly genes involved in environmental sensing. When the strains were grown in coculture, there was a modest but significant change in their individual transcription patterns compared to those in pure culture. Each strain sensed the presence of the other and responded in a specific manner, which points to fine intraspecific transcriptomic modulation. ; The group of J.A. is funded by grant CGL2012-39627-C03-01 from the Spanish Ministry of Economy and Competitiveness (MINECO), which is cofinanced with FEDER support from the European Union. P.G.-T. was an FPI-MINECO fellow. Research by the group of T.G. is funded in part by a grant from the ...

The application of tandem MALDI-TOF MS screening with 16S rRNA gene sequencing of selected isolates has been demonstrated to be an excellent approach for retrieving novelty from large-scale culturing. The application of such methodologies in different hypersaline samples allowed the isolation of the culture-recalcitrant Salinibacter ruber second phylotype (EHB-2) for the first time, as well as a new species recently isolated from the Argentinian Altiplano hypersaline lakes. In this study, the genome sequences of the different species of the phylum Rhodothermaeota were compared and the genetic repertoire along the evolutionary gradient was analyzed together with each intraspecific variability. Altogether, the results indicated an open pan-genome for the family Salinibacteraceae, as well as the codification of relevant traits such as diverse rhodopsin genes, CRISPR-Cas systems and spacers, and one T6SS secretion system that could give ecological advantages to an EHB-2 isolate. For the new Salinibacter species, we propose the name Salinibacter altiplanensis sp. nov. (the designated type strain is AN15T = CECT 9105T = IBRC-M 11031T). ; This study was funded by the Spanish Ministry of Economy projects CGL2012-39627-C03-03 and CLG2015-66686-C3-1-P (to RRM), CLG2015-66686-C3-3-P (to JA), which were also both supported with European Regional Development Fund (FEDER) funds. RA was financed by the Max Planck Society. KTK's research was supported, in part, by the U.S. National Science Foundation (Award No. 1241046). TVP acknowledges a pre-doctoral fellowship (Nr BES-2013-064420) from the Ministerio de Economía y Competitividad of the Spanish Government. The authors also acknowledge the economic support and unconditional scientific interest of Lipotrue SL and Deep Blue Sea SL.

Accelerated postnatal growth is a potentially modifiable risk factor for future obesity. To study how specific breast milk components contribute to early growth and obesity risk, we quantified one-carbon metabolism-related metabolites in human breast milk and found an inverse association between milk betaine content and infant growth. This association was replicated in an independent and geographically distinct cohort. To determine the potential role of milk betaine in modulating offspring obesity risk, we performed maternal betaine supplementation experiments in mice. Higher betaine intake during lactation increased milk betaine content in dams and led to lower adiposity and improved glucose homeostasis throughout adulthood in mouse offspring. These effects were accompanied by a transient increase in Akkermansia spp. abundance in the gut during early life and a long-lasting increase in intestinal goblet cell number. The link between breast milk betaine and Akkermansia abundance in the gut was also observed in humans, as infants exposed to higher milk betaine content during breastfeeding showed higher fecal Akkermansia muciniphila abundance. Furthermore, administration of A. muciniphila to mouse pups during the lactation period partially replicated the effects of maternal breast milk betaine, including increased intestinal goblet cell number, lower adiposity, and improved glucose homeostasis during adulthood. These data demonstrate a link between breast milk betaine content and long-term metabolic health of offspring. ; This work was supported by grants from Ajinomoto Innovation Alliance Program (Ajinomoto 2015-2017) to CL, EFSD/Lilly programme to C.L., and the Spanish Government (SAF-2017-88005-R to C.L. and BFU2017-89336-R to M.V.). D.S.-I. and J.C.J.-C. are Miguel Servet investigators (Carlos III National Institute of Health, Spain). The MILK Study is supported by NIH grant R01-HD080444 to D.A.F. and E.W.D. Mead Johnson Nutrition provided financial support to D.A.F. for breast milk collection, but had no role in study design, study results, or manuscript content. M.C.C. and I.G.-M. acknowledge support from European Research Council under the European Union's Horizon 2020 research and innovation programme (ERC Starting Grant 639226).