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.

Bacterial communities in an ultrapure water containing storage tank of a power plant.

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.

Microbiological investigation of an industrial ultra pure supply water plant using cultivation-based and cultivation-independent methods.

Ultra pure waters (UPW), characterized by extremely low salt and nutrient concentrations, can suffer from microbial contamination which causes biofouling and biocorrosion, possibly leading to reduced lifetime and increased operational costs. Samples were taken from an ultra pure supply water producing plant of a power plant. Scanning electron microscopic examination was carried out on the biofilms formed in the system. Biofilm, ion exchange resin, and water samples were characterized by culture-based methods and molecular fingerprinting (terminal restriction fragment length polymorphism [T-RFLP] analysis and molecular cloning). Identification of bacteria was based on 16S rDNA sequence comparison. A complex microbial community structure was revealed. Nearly 46% of the clones were related to as yet uncultured bacteria. The community profiles of the water samples were the most diverse and most of bacteria were recruited from bacterial communities of tube surface and ion exchange resin biofilms. Microbiota of different layers of the mixed bed ion exchange resin showed the highest similarity. Most of the identified taxa (dominated by ß-Proteobacteria) could take part in microbially influenced corrosion.