1 3 Arch Microbiol DOI 10.1007/s00203-017-1379-9 ORIGINAL PAPER The effect of reconstruction works on planktonic bacterial diversity of a unique thermal lake revealed by cultivation, molecular cloning and next generation sequencing Gergely Krett 1 · Attila Szabó 1 · Tamás Felföldi 1 · Károly Márialigeti 1 · Andrea K. Borsodi 1 Received: 28 November 2016 / Revised: 1 March 2017 / Accepted: 11 April 2017 © Springer-Verlag Berlin Heidelberg 2017 Keywords Freshwater bacteria · Thermal lake · Anthropogenic disturbance · Cultivation · Molecular cloning · Pyrosequencing Introduction Despite the relatively insignificant Earth’s surface cover- age, freshwater environments offer essential ecosystem ser- vices to human populations by providing water for drink- ing, bathing, agriculture, industry and recreation. Owing to their connective role of atmospheric and terrestrial pro- cesses and sensitiveness to environmental changes, they are rather vulnerable which makes them good indicator at local and global scale (Williamson et al. 2008). The first recognition about the key role of bacterial communities in the biogeochemical cycles of freshwater environments was made by Lindeman in the 1940s (Lindeman 1942). Since then several studies confirmed the importance of bacte- ria in the nutrient cycles of freshwater environments (e.g. Cotner and Biddanda 2002), and owing to the increasingly sophisticated molecular biological methods a wide range of diversity was also revealed from these habitats (Zwart et al. 2002; Wu et al. 2007; Vaz-Moreira et al. 2011). These examinations pointed out that although significant differ- ences could be between bacterial communities inhabiting different lakes, there are “typical freshwater bacteria” dis- tributed worldwide in freshwater environments (Newton et al. 2011). Phyla Proteobacteria, Actinobacteria, Bacte- roidetes, Cyanobacteria and Verrucomicrobia includes the most widespread freshwater bacteria of which Betaproteo- bacteria and Actinobacteria are the most abundant in lake epilimnia according to Fluorescent In Situ Hybridization (FISH) based studies (Zwart et al. 2002; Allgaier and Gros- sart 2006; Wu et al. 2006). Although Actinobacteria related Abstract The aim of this study was to gain detailed infor- mation about the diversity of planktonic bacterial commu- nities of a worldwide special peat bedded natural thermal spa lake, and to reveal the effect of a lake wall reconstruc- tion work. To compare the efficiency of different methods used for analyzing bacterial diversity, cultivation, molecu- lar cloning and pyrosequencing were applied simultane- ously. Despite the almost unchanged physical–chemical parameters and cell count values of lake water, remarkable differences were observed in the planktonic bacterial com- munity structures during and after the reconstruction by all applied microbiological approaches. Rhodobacter sp. was found to be one of the most abundant community mem- bers during the works probably due to the sediment stirring effect of the reconstruction. Following the reconstruction higher diversity was detected than during the works by all approaches. Bacterial strains related to species Chryseo- bacterium and Exiguobacterium, furthermore sequences related to Arcobacter, Gemmobacter and MWH-UniP1 aquatic group were identified in the highest proportion at that time. Although the differences revealed by cultivation based and independent community structures were signifi- cant, only minor disparities were found by molecular clon- ing and next generation sequencing techniques. Communicated by Shuang-Jiang Liu. Electronic supplementary material The online version of this article (doi:10.1007/s00203-017-1379-9) contains supplementary material, which is available to authorized users. * Andrea K. Borsodi borsodi.andrea@ttk.elte.hu 1 Department of Microbiology, Eötvös Loránd University, Pázmány P. sétány 1/C, 1117 Budapest, Hungary