Freshwater plankton as a habitat for hygienically relevant microorganisms

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Plankton in surface waters provides a large surface which can be colonized by biofilms. These can harbour hygienically relevant microorganisms which can be transported by plankton organisms as vectors. This has been shown for Vibrio species, but much less is known about other organisms and for freshwater, while first results indicate a similar situation. Furthermore, the organisms can enter a viable but non culturable (VBNC) state and will not be detected by conventional culture methods. This poses a hygienic risk when the water is used for drinking water production and/or for recreational purposes. In this project, colonization of both (living and dead) locally typical phytoplankton and Zooplankton by target organisms will be investigated in a mesotrophic lake (Baldeneysee). Defined spatio-temporal sampling with sampling points according to possible input sites and events of target bacteria will be performed. Target organisms are fecal indicators (E. coli, enterococci, C. perfringens) and pathogens (Campylobacter spp., P. aeruginosa, Legionella spp. and Aeromonas spp.) Particular attention is payed to the VBNC state which will be detected using molecular biological methods. Viability will be determined by cultivation as well as by direct viable count, membrane integrity determination, FISH and real-time PCR for Legionella spp. Results of this project will contribute to risk assessment.