Dataset Information

The underlying process of early ecological and genetic differentiation in a facultative mutualistic Sinorhizobium meliloti population.

ABSTRACT: The question of how genotypic and ecological units arise and spread in natural microbial populations remains controversial in the field of evolutionary biology. Here, we investigated the early stages of ecological and genetic differentiation in a highly clonal sympatric Sinorhizobium meliloti population. Whole-genome sequencing revealed that a large DNA region of the symbiotic plasmid pSymB was replaced in some isolates with a similar synteny block carrying densely clustered SNPs and displaying gene acquisition and loss. Two different versions of this genomic island of differentiation (GID) generated by multiple genetic exchanges over time appear to have arisen recently, through recombination in a particular clade within this population. In addition, these isolates display resistance to phages from the same geographic region, probably due to the modification of surface components by the acquired genes. Our results suggest that an underlying process of early ecological and genetic differentiation in S. meliloti is primarily triggered by acquisition of genes that confer resistance to soil phages within particular large genomic DNA regions prone to recombination.

SUBMITTER: Toro N

PROVIDER: S-EPMC5429615 | biostudies-literature | 2017 Apr

REPOSITORIES: biostudies-literature

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The underlying process of early ecological and genetic differentiation in a facultative mutualistic Sinorhizobium meliloti population.

Toro Nicolás N Villadas Pablo J PJ Molina-Sánchez María Dolores MD Navarro-Gómez Pilar P Vinardell José M JM Cuesta-Berrio Lidia L Rodríguez-Carvajal Miguel A MA

Scientific reports 20170406 1

The question of how genotypic and ecological units arise and spread in natural microbial populations remains controversial in the field of evolutionary biology. Here, we investigated the early stages of ecological and genetic differentiation in a highly clonal sympatric Sinorhizobium meliloti population. Whole-genome sequencing revealed that a large DNA region of the symbiotic plasmid pSymB was replaced in some isolates with a similar synteny block carrying densely clustered SNPs and displaying ...[more]

PMID: 28386109

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Project description:Interactions between photosynthetic microalgae and bacteria impact the physiology of both partners, which influence the fitness and ecological trajectories of each partner in an environmental context-dependent manner. Thermal tolerance of Chlamydomonas reinhardtii can be enhanced through a mutualistic interaction with vitamin B12 (cobalamin)-producing Sinorhizobium meliloti. Here, we used label-free quantitative proteomics to reveal the metabolic networks altered by the interaction under normal and high temperatures. We created a scenario where the growth of Sinorhizobium requires carbon provided by Chlamydomonas for growth in co-cultures, and survival of Chlamydomonas under high temperatures relies on cobalamin and possibly other metabolites produced by Sinorhizobium. Differential abundance analysis identified proteins produced by each partner in co-cultures compared to mono-cultures at each temperature. Proteins involved in cobalamin production by Sinorhizobium increased in the presence of Chlamydomonas under elevated temperatures, whereas in Chlamydomonas, there was an increase in cobalamin-dependent methionine synthase and certain proteins associated with methylation reactions. Co-cultivation and heat stress strongly modulated the central metabolism of both partners as well as various transporters that could facilitate nutrient cross-utilization. Co-cultivation modulated expression of various components of two- or one-component signal transduction systems, transcriptional activators/regulators, or sigma factors, suggesting complex regulatory networks modulate the interaction in a temperature-dependent manner. Notably, heat and general stress-response and antioxidant proteins were upregulated in co-cultures, suggesting that the interaction is inherently stressful to each partner despite the benefits of mutualism. Our results shed insight into the metabolic tradeoffs required for mutualism and how metabolic networks are modulated by elevated temperature.ImportancePhotosynthetic microalgae are key primary producers in aquatic ecosystems, playing an important role in the global carbon cycle. Nearly every alga lives in association with a diverse community of microorganisms that influence each other and their metabolic activities or survival. One chemical produced by bacteria that influence algae is vitamin B12, an enzyme cofactor used for a variety of metabolic functions. The alga Chlamydomonas reinhardtii benefits from vitamin B12 produced by Sinorhizobium meliloti by producing the amino acid methionine under high temperatures which are required for Chlamydomonas thermotolerance. Yet, our understanding of this interaction under normal and stressful temperatures is poor. Here, we used quantitative proteomics to identify differentially expressed proteins to reveal metabolic adjustments made by Chlamydomonas and Sinorhizobium that could facilitate this mutualism. These findings will enhance our understanding of how photosynthetic algae and their associated microbiomes will respond as global temperatures increase.

Dataset Information

The underlying process of early ecological and genetic differentiation in a facultative mutualistic Sinorhizobium meliloti population.

Publications

The underlying process of early ecological and genetic differentiation in a facultative mutualistic Sinorhizobium meliloti population.

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