Application of special oligotrophic media for cultivation of bacterial communities originated from ultrapure water.

Because of the selectivity of the commonly used media it is very difficult to cultivate bacteria inhabiting ultrapure waters under laboratory conditions. In this study 5 new media (synthetic and complex) were developed to reveal bacterial community of the ultrapure water originated from the water purification system of a Hungarian power plant which was studied already with using traditional media. Composition of the new media tends to reproduce the nutrient deficient conditions of the investigated water, therefore media were highly oligotrophic. Altogether 122 bacterial strains were isolated from the 5 different media. Based on ARDRA grouping 27 strains were chosen for the partial 16S rRNA gene sequence analysis. The results showed that the applied media strongly influence the composition of the cultivable bacterial community. A larger scale of α-Proteobacteria (Mesorhizobium spp., Ancylobacter sp., Methylobacterium sp.) and many Actinobacteria (Leifsonia sp., Microbacterium spp., Mycobacterium spp.) could be isolated from the same ultrapure water system than with any other cultivation methods or media applied before. Moreover, two novel bacterial taxa could be isolated from the studied water purification system.