TY - JOUR T1 - Fine-scale evolution: genomic, phenotypic and ecological differentiation in two coexisting Salinibacter ruber strains. JF - The ISME journal Y1 - 2010 A1 - Peña, Arantxa A1 - Teeling, Hanno A1 - Huerta-Cepas, Jaime A1 - Santos, Fernando A1 - Yarza, Pablo A1 - Brito-Echeverría, Jocelyn A1 - Lucio, Marianna A1 - Schmitt-Kopplin, Philippe A1 - Meseguer, Inmaculada A1 - Schenowitz, Chantal A1 - Dossat, Carole A1 - Barbe, Valerie A1 - Joaquín Dopazo A1 - Rosselló-Mora, Ramon A1 - Schüler, Margarete A1 - Glöckner, Frank Oliver A1 - Amann, Rudolf A1 - Gabaldón, Toni A1 - Antón, Josefa AB -

Genomic and metagenomic data indicate a high degree of genomic variation within microbial populations, although the ecological and evolutive meaning of this microdiversity remains unknown. Microevolution analyses, including genomic and experimental approaches, are so far very scarce for non-pathogenic bacteria. In this study, we compare the genomes, metabolomes and selected ecological traits of the strains M8 and M31 of the hyperhalophilic bacterium Salinibacter ruber that contain ribosomal RNA (rRNA) gene and intergenic regions that are identical in sequence and were simultaneously isolated from a Mediterranean solar saltern. Comparative analyses indicate that S. ruber genomes present a mosaic structure with conserved and hypervariable regions (HVRs). The HVRs or genomic islands, are enriched in transposases, genes related to surface properties, strain-specific genes and highly divergent orthologous. However, the many indels outside the HVRs indicate that genome plasticity extends beyond them. Overall, 10% of the genes encoded in the M8 genome are absent from M31 and could stem from recent acquisitions. S. ruber genomes also harbor 34 genes located outside HVRs that are transcribed during standard growth and probably derive from lateral gene transfers with Archaea preceding the M8/M31 divergence. Metabolomic analyses, phage susceptibility and competition experiments indicate that these genomic differences cannot be considered neutral from an ecological perspective. The results point to the avoidance of competition by micro-niche adaptation and response to viral predation as putative major forces that drive microevolution within these Salinibacter strains. In addition, this work highlights the extent of bacterial functional diversity and environmental adaptation, beyond the resolution of the 16S rRNA and internal transcribed spacers regions.The ISME Journal advance online publication, 18 February 2010; doi:10.1038/ismej.2010.6.

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