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.
Thermal baths are unique aquatic environments combining a wide variety of natural and anthropogenic ecological factors, which also appear in their microbiological state. There is limited information on the microbiology of thermal baths in their complexity, tracking community shifts from the thermal wells to the pools. In the present study, the natural microbial community of well and pool waters in Gellért bath was studied in detail by cultivation-based techniques. To isolate bacteria, 10% R2A and minimal synthetic media (with “bath water”) with agar–agar and gellan gum were used after prolonged incubation time; moreover, polyurethane blocks covered with media were also applied. Strains were identified by sequencing their 16S rRNA gene after grouping them by amplified rDNA restriction analysis. From each sample, the dominance of Alphaproteobacteria was characteristic though their diversity differed among samples. Members of Actinobacteria, Firmicutes, Beta- and Gamma-proteobacteria, Deinococcus–Thermus, and Bacteroidetes were also identified. Representatives of Deinococcus–Thermus phylum appeared only in the pool water. The largest groups in the pool water belonged to the Tistrella and Chelatococcus genera. The most dominant member in the well water was a new taxon, its similarity to Hartmannibacter diazotrophicus as closest relative was 93.93%.
Ultrapure waters (UPWs) containing low levels of organic and inorganic compounds provide extreme environment. On contrary to that microbes occur in such waters and form biofilms on surfaces, thus may induce corrosion processes in many industrial applications. In our study, refined saltless water (UPW) produced for the boiler of a Hungarian power plant was examined before and after storage (sampling the inlet [TKE] and outlet [TKU] waters of a storage tank) with cultivation and culture independent methods. Our results showed increased CFU and direct cell counts after the storage. Cultivation results showed the dominance of aerobic, chemoorganotrophic α-Proteobacteria in both samples. In case of TKU sample, a more complex bacterial community structure could be detected. The applied molecular method (T-RFLP) indicated the presence of a complex microbial community structure with changes in the taxon composition: while in the inlet water sample (TKE) α-Proteobacteria (Sphingomonas sp., Novosphingobium hassiacum) dominated, in the outlet water sample (TKU) the bacterial community shifted towards the dominance of α-Proteobacteria (Rhodoferax sp., Polynucleobacter sp., Sterolibacter sp.), CFB (Bacteroidetes, formerly Cytophaga-Flavobacterium-Bacteroides group) and Firmicutes. This shift to the direction of fermentative communities suggests that storage could help the development of communities with an increased tendency toward corrosion.