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.
This study provides a comprehensive microbiological survey of three drinking water networks applying different water treatment processes. Variability of microbial communities was assessed by cultivation-based [nitrifying, denitrifying most probable number (MPN) heterotrophic plate count] and sequence-aided terminal restriction fragment length polymorphism (T-RFLP) analysis. The effect of microbial community composition on nitrifying MPN values was revealed. The non-treated well water samples showed remarkable differences to their corresponding distribution systems regarding low plate count, nitrifying MPN, and the composition of microbial communities, which increased and changed, respectively, in distribution systems. Environmental factors, such as pH, total inorganic nitrogen content (ammonium and nitrite concentration), and chlorine dioxide treatment had effect on microbial community compositions. The revealed heterogeneous nitrifying population achieved remarkable nitrification, which occurred at low ammonium concentration (14–51 μM) and slightly alkaline pH 7.7–7.9 in chlorine dioxide disinfected water networks. No change was observed in nitrification-generated nitrate concentration, although nitrate-reducing (and denitrifying) bacteria were present with low MPN and characterized by sequence-aided T-RFLP. The community structures of water samples partially changed in nitrifying enrichments and had influence on the generated nitrifying, especially nitrite-oxidizing MPN regarding the facilitated growth of nitrate-reducing bacteria and even methanogenic archaea beside ammonia-oxidizing microorganisms and nitrite-oxidizing bacteria.
In this study, changes in the bacterial community composition of the well waters of Harkány Spa were examined. Physical and chemical properties of mixing subsurface cold and thermal karst waters were correlated to shifts in bacterial community structures analyzed by denaturing gradient gel electrophoresis (DGGE) and principal component analysis (PCA). In addition, mineral components of the pellets were investigated by scanning electron microscopy. Samples from the effluent waters of Büdöstapolca I and II, Matty and Thermal VI wells were taken seasonally in 2007 and 2008. The comparison of the results of DGGE and PCA analyses showed that bacterial communities from the Büdöstapolca wells were distinct from those of Matty and Thermal VI, but seasonal changes were not detected. According to the phylogenetic analysis of the excised DGGE bands, presence of chemolithotrophic Proteobacteria (Thiobacillus, Thiothrix, and distant relatives of Sulfurospirillum) were typical in the Büdöstapolca wells, while members of Actinobacteria (Plantibacter, Actinobacterium, Microbacterium) and Firmicutes (Planococcus) were characteristic to the Matty and Thermal VI wells. In the pellets pyrite framboid crystals were observed by electron microscopy, which are minerals known to be biologically induced by dissimilatory iron- and sulfur (sulfate)-reducing bacteria.
Lake Hévíz is a unique thermal spa located in Hungary. Owing to the thermal springs nourishing the lake, it has a relatively rapid water turnover. In spring 2011 a comprehensive embankment reconstruction was performed to preserve the water supply of the surrounding wetland habitats. The physical and chemical parameters as well as the planktonic microbial communities were studied with special respect to the effect of the disturbance of the water of Lake Hévíz. According to the abiotic components, both temporal and spatial differences were revealed with the exception of autumn samples. The reconstruction resulted in a short term but dramatic alteration of the total planktonic bacterial and cyanobacterial community structures as revealed by denaturing gradient gel electrophoresis. In addition, greater seasonal than spatial differences of bacterial communities were also observed. Planktonic bacterial community composition of Lake Hévíz included mainly typical freshwater species within phylum Actinobacteria, Chloroflexi, Cyanobacteria and class Alpha-, Beta- and Gamma-proteobacteria. Most of them were aerobic or facultative anaerobic heterotrophic but chemolitotrophic (e.g. Thiobacillus) or photolithotrophic (e.g. Cyanobacteria and Chloroflexi) autotrophic microbes were also identified.
The effect of several easily degradable substrates, such as protein, starch and sunflower oil was investigated on the bacterial community of a laboratory-scale biogas model system. Besides measuring gas yield, Denaturing Gradient Gel Electrophoresis (DGGE), Phospholipids Fatty Acid Analysis (PLFA) for Bacteria and T-RFLP analysis of the mcrA gene for Archaea were used. The community of the examined biogas reactors adapted to the new substrates through a robust physiological reaction followed by moderate community abundance shifts. Gas yield data clearly demonstrated the physiological adaptation to substrate shifts. Statistical analysis of DNA and chemotaxonomic biomarkers revealed community abundance changes. Sequences gained from DGGE bands showed the dominance of the phyla Bacteroidetes and the presence of Firmicutes (Clostridia) and Thermotogae. This was supported by the detection of large amounts of branched 15-carbon non-hydroxy fatty acids in PLFA profiles, as common PLFA markers of the Bacteroidetes group. Minor abundance ratios changes were observed in the case of Archaea in accordance with changes of the fed substrates.
Lake Hévíz is the largest natural warm water lake of Europe. The curative mud of the lake comprises volcanic and marsh components although their species composition is hardly known yet. The aim of the present study was to gain information about the distribution and species diversity of bacterial communities inhabiting the sediment of Lake Hévíz using cultivation-based and molecular cloning methods. Samples from two depths and locations were taken in 2004 and 2007. Representatives of the altogether 255 bacterial isolates were affiliated with the phyla Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes. The most abundant groups belonged to the genus Bacillus (Firmicutes). Many of Lake Hévíz isolates showed the highest sequence similarity to bacteria known to be plant associated or members of normal human microbiota as well as participating in decomposition of highly resistant organic materials. In the three clone libraries, phylotypes belonging to altogether different phyla (Firmicutes, Actinobacteria, Proteobacteria, Bacteroidetes, Cyanobacteria, Chlorobi, Chloroflexi, Deferribacteres, Nitrospirae, Spirochaetes and Verrucomicrobia) were revealed from which members of Gammaproteobacteria and Cyanobacteria proved to be the most abundant. Regardless of the sampling times and methodology used, high spatial heterogeneities of bacterial community structures were characteristic of the sediment of Lake Hévíz.
Karst areas have great environmental importance as sources of subsurface water and often maintain very sensitive ecosystems. In recent years, increasing number of microbiological studies focused on the bacterial communities of karst soils. In this study, diversity examinations on two distinct Hungarian karst areas, Aggtelek and Tapolca, were performed using parallel cultivation and molecular cloning methods. The phylogenetic affiliation of bacterial strains and molecular clones was determined based on their 16S rRNA gene sequences. Bacterial isolates were identified as members of the phyla Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes. Besides the taxa identified by cultivation, members of the phyla Chloroflexi, Cyanobacteria, Acidobacteria, Verrucomicrobia, and Gemmatimonadetes were detected by the cloning. The difference in the composition of soil bacterial communities was related to geographic locations and soil types. Both the highest and the lowest bacterial diversities were detected in samples from Aggtelek National Park, characterized by Leptic Luvisol and Rendzic Leptosol soil types. The difference in the composition of bacterial communities between Rendzic Leptosol and Leptic Phaeozem soil types at Tapolca could be the result of human impacts.
Geothermal wells characterized by thermal waters warmer than 30°C can be found in more than 65% of the area of Hungary. The examined thermal wells located nearby Szarvas are used for heating industrial and agricultural facilities because of their relatively high hydrocarbon content. The aim of this study was to reveal the prokaryotic community structure of the water of SZR18, K87 and SZR21 geothermal wells using molecular cloning methods and Denaturing Gradient Gel Electrophoresis (DGGE). Water samples from the outflow pipes were collected in 2012 and 2013. The phylogenetic distribution of archaeal molecular clones was very similar in each sample, the most abundant groups belonged to the genera Methanosaeta, Methanothermobacter and Thermofilum. In contrast, the distribution of bacterial molecular clones was very diverse. Many of them showed the closest sequence similarities to uncultured clone sequences from similar thermal environments. From the water of the SZR18 well, phylotypes closely related to genera Fictibacillus and Alicyclobacillus (Firmicutes) were only revealed, while the bacterial diversity of the K87 well water was much higher. Here, the members of the phyla Thermodesulfobacteria, Proteobacteria, Nitrospira, Chlorobi, OP1 and OPB7 were also detected besides Firmicutes.
Karst areas belong to the most exposed terrestrial ecosystems, therefore their study have a priority task in Hungary, as well. The aim of this study was to compare the structure, activity and diversity of soil microbial communities from two distinct Hungarian karst areas (Aggtelek NP and Tapolca-basin). Soil samples were taken three times from 6 distinct sites, from different depths. Soil microbial biomass C (MBC), microbial biomass N (MBN), basal respiration (BRESP) and substrate induced respiration (SIR) were measured. The phylogenetic diversity of bacterial communities was compared by Denaturing Gradient Gel Electrophoresis (DGGE). The highest MBC, MBN, BRESP and SIR values were measured in the rendzina soil from Aggtelek. On the basis of biomass and respiration measurements, microbial communities differentiated mainly according to soil depths whereas DGGE profiles of bacterial communities resulted in groups mainly according to sampling sites.