Insight into the hidden bacterial diversity of Lake Balaton, Hungary

In the present study, the prokaryotic community structure of the water of Lake Balaton was investigated at the littoral region of three different points (Tihany, Balatonmáriafürdő and Keszthely) by cultivation independent methods [next-generation sequencing (NGS), specific PCRs and microscopy cell counting] to check the hidden microbial diversity of the lake. The taxon-specific PCRs did not show pathogenic bacteria but at Keszthely and Máriafürdő sites extended spectrum beta-lactamase-producing microorganisms could be detected. The bacterial as well as archaeal diversity of the water was high even when many taxa are still uncultivable. Based on NGS, the bacterial communities were dominated by Proteobacteria, Bacteroidetes and Actinobacteria, while the most frequent Archaea belonged to Woesearchaeia (Nanoarchaeota). The ratio of the detected taxa differed among the samples. Three different types of phototrophic groups appeared: Cyanobacteria (oxygenic phototrophic organisms), Chloroflexi (anaerobic, organotrophic bacteria) and the aerobic, anoxic photoheterotrophic group (AAPs). Members of Firmicutes appeared only with low abundance, and Enterobacteriales (order within Proteobacteria) were present also only in low numbers in all samples.