The biogeography of prokaryotes and the effect of geographical barriers as evolutionary constraints are currently subjected to great debate. Some clear-cut evidence for geographic isolation has been obtained by genetic methods but, in many cases, the markers used are too coarse to reveal subtle biogeographical trends. Contrary to eukaryotic microorganisms, phenotypic evidence for allopatric segregation in prokaryotes has never been found. Here we present, for the first time, a metabolomic approach based on ultrahigh resolution mass spectrometry to reveal phenotypic biogeographical discrimination. We demonstrate that strains of the cosmopolitan extremophilic bacterium Salinibacter ruber, isolated from different sites in the world, can be distinguished by means of characteristic metabolites, and that these differences can be correlated to their geographical isolation site distances. The approach allows distinct degrees of discrimination for isolates at different geographical scales. In all cases, the discriminative metabolite patterns were quantitative rather than qualitative, which may be an indication of geographically distinct transcriptional or posttranscriptional regulations.

Six strains of extremely halophilic bacteria were isolated from several crystallizer ponds of the Maras solar salterns in the Peruvian Andes. On the basis of 16S rRNA gene sequence similarity, G+C contents and DNA-DNA hybridization results, the six isolates constituted a genomically homogeneous group affiliated with the Gammaproteobacteria. The closest relatives were members of the halophilic genera Halovibrio and Halospina, which showed 16S rRNA gene sequence similarities below 97 % and whole-genome hybridization levels below 33 % for the type strain, 7Sm5 T. From the genomic and phenotypic properties of the six novel isolates and phylogenetic reconstruction based on 16S rRNA gene sequence analysis, they can be considered to represent a novel genus within the Gammaproteobacteria. On the basis of the taxonomic study, a novel genus, Salicola gen. nov., is proposed containing the single species Salicola marasensis sp. nov., which is the type species. The type strain of Salicola marasensis is 7Sm5 T (=CECT 7107 T =CIP 108835 T). The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains 7Sm5 T , 2Sb7, 7Sa10, 7Sm7, 7Mb1 and 5Ma3 are DQ019934, DQ019935 and DQ087259-DQ087262, respectively. Details of the reference sequences used in the construction of Fig. 1 are available as supplementary material in IJSEM Online.

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