ena-STUDY-TUM-23-05-2017-17:11:28:884-405
Temporal dynamics of the toxic cyanobacterial community composition and toxin presence in two South German lakes
Bacterioplankton plays an essential role in aquatic ecosystems, and cyanobacteria are an influential part of the microbiome in many water bodies. In freshwaters used for recreational activities or drinking water, toxic cyanobacteria cause concerns due to the risk of intoxication with cyanotoxins, such as microcystins. In this study, we aimed to unmask relationships between toxicity, cyanobacterial community composition, and environmental factors. At the same time, we assessed the suitability of a genetic marker to serve as toxicity proxy and aimed to expose the main microcystin producer bacterium. We used Illumina MiSeq sequencing to assess bacterioplankton and perform an in depth analysis of the cyanobacterial community composition in two recreational lakes in South Germany during the cyanobacterial bloom period. We quantified a microcystin biosynthesis gene (mcyB) using qPCR and linked this information with microcystin concentration using HPLC and ELISA to assess toxicity. Microcystin biosynthesis gene (mcyE)-clone libraries were used to determine the origin of toxicity genes. Both lakes displayed distinct bacterial community compositions during the sampling period despite sharing a large fraction of their microbiome (about three quarters of all bacterial OTUs). Proteobacteria, Actinobacteria, and Cyanobacteria dominated Lake Klostersee while Cyanobacteria prevailed in Lake Bergknappweiher. The cyanobacterial community composition was highly dynamic in both lakes, and temporal variations were most evident at the lowest taxonomic level. In both lakes, we witnessed a diversification of dominant cyanobacterial genera. Microcystin concentration correlated positively with total phosphorus and mcyB copy number. However, mcyB copy number was not a reliable signal for bloom toxicity. We identified low abundant Microcystis sp. as the only microcystin producer in both lakes. Therefore, risk assessment efforts need to take into account the fact that dominant cyanobacterial taxa did not contribute to the microcystin contamination of the blooms observed.
Bacterioplankton plays an essential role in aquatic ecosystems, and cyanobacteria are an influential part of the microbiome in many water bodies. In freshwaters used for recreational activities or drinking water, toxic cyanobacteria cause concerns due to the risk of intoxication with cyanotoxins, such as microcystins. In this study, we aimed to unmask relationships between toxicity, cyanobacterial community composition, and environmental factors. At the same time, we assessed the suitability of a genetic marker to serve as toxicity proxy and aimed to expose the main microcystin producer bacterium. We used Illumina MiSeq sequencing to assess bacterioplankton and perform an in depth analysis of the cyanobacterial community composition in two recreational lakes in South Germany during the cyanobacterial bloom period. We quantified a microcystin biosynthesis gene (mcyB) using qPCR and linked this information with microcystin concentration using HPLC and ELISA to assess toxicity. Microcystin biosynthesis gene (mcyE)-clone libraries were used to determine the origin of toxicity genes. Both lakes displayed distinct bacterial community compositions during the sampling period despite sharing a large fraction of their microbiome (about three quarters of all bacterial OTUs). Proteobacteria, Actinobacteria, and Cyanobacteria dominated Lake Klostersee while Cyanobacteria prevailed in Lake Bergknappweiher. The cyanobacterial community composition was highly dynamic in both lakes, and temporal variations were most evident at the lowest taxonomic level. In both lakes, we witnessed a diversification of dominant cyanobacterial genera. Microcystin concentration correlated positively with total phosphorus and mcyB copy number. However, mcyB copy number was not a reliable signal for bloom toxicity. We identified low abundant Microcystis sp. as the only microcystin producer in both lakes. Therefore, risk assessment efforts need to take into account the fact that dominant cyanobacterial taxa did not contribute to the microcystin contamination of the blooms observed.