Microbial ecology is the younger sub-discipline of ecology, but its scope is clearly\ud immense. Microorganisms’ specificities represent a major hurdle to the application\ud of traditional ecological approaches. Recently, the opportunity to apply ecological\ud principles to microorganisms was suggested. It is assumed that existing principles\ud might apply, but that they are probably also driven by specific principles.\ud Microorganisms have varying metabolic abilities and are classified as generalists or\ud specialists. We hypothesised that contrasting metabolic properties may drive\ud genotypic distribution. Model generalist and specialist genera were selected and\ud distribution patterns along the salinity gradient of the River Colne estuary studied.\ud Two models were studied in detail, Desulfobulbus a versatile sulphate-reducing\ud bacterial (SRB) genus and Methanosaeta, a strict aceticlastic methanogenic archaea\ud (MA). Isolation of Methanosaeta was attempted in order to link phenotypes to\ud genotypic distribution. Two other models were also studied: Methanosarcina the\ud most versatile MA genus and Desulfobacter a metabolically restricted SRB genus.\ud Denaturing gel gradient electrophoresis (DGGE) and clone libraries analyses were\ud used to determine genotypic distribution patterns.\ud Methanosaeta have proven to be highly recalcitrant to isolation. Adjustments to\ud commonly used anaerobic culturing methods allowed the obtention of Methanosaeta\ud colonies. In contrast to previous studies, colonies were successfully transferred into\ud liquid medium, and growth of pure clonal cultures confirmed.\ud Desulfobulbus genotypic distribution pattern was previously shown to be sequential\ud along the estuary. Contrastingly, Methanosaeta genotypic distribution pattern was\ud found to be monotonic. Furthermore, active genotypes distribution was also found\ud monotonic, with an apparent general increase in activity with decreasing salinity.\ud Distribution patterns of the four different genera confirmed this trend. The\ud generalists were both shown to have sequential distribution patterns. Contrastingly,\ud the specialists were both shown to have monotonic distribution patterns.\ud These results confirm the hypothesis that genotypic distribution patterns microbial\ud communities structure are strongly driven by microorganisms’ metabolic properties\ud and adaptative potential
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