Global phylogeography of pelagic Polynucleobacter bacteria: restricted geographic distribution of subgroups, isolation by distance and influence of climate.

摘要: The free-living planktonic freshwater bacterium Polynucleobacter necessarius subspecies asymbioticus (> 99% 16S rRNA similarity) represents a taxon with cosmopolitan distribution and apparently ubiquitous occurrence in lentic habitats. We tested for intra-taxon biogeographic patterns by combining cultivation-independent cultivation methods. A culture collection of 204 strains isolated from globally distributed habitats (Arctic to Antarctica) was investigated phylogeographic based on sequences two markers, the 16S–23S internal transcribed spacers glutamine synthetase gene (glnA). Genetic distance between isolates showed significant geographic distance-decay both suggesting that an isolation-by-distance mechanism influences global phylogeography. Furthermore, couple subgroups restricted distributions. Strains one subgroup were exclusively obtained tropical sites four continents (pantropical subgroup). Cultivation-independent methods used confirm distributions subgroups. pantropical could be detected 63% but not any 121 European samples. Physiological tests indicated almost all failed grow at temperatures 4°C, while affiliated other good growth this temperature. This suggests thermal adaptation is involved structuring population.