Presence and survival of selected pathogens (Legionella sp., Aeromonas sp.) in lakes of varying degrees of eutrophication

Bacteria belonging to genus Legionella i Aeromonas are usually an autochthonous component of the microbial community inhabiting various aquatic environments. The presence of these potentially pathogenic bacteria, especially in high abundance, is assumed to be a serious threat to human health. Occurrence of both genera is promoted by elevated water temperature. Due to global warming, the short-term occurrence of thermal conditions favorable to the development of Legionella spp. and Aeromonas spp. in lakes of the temperate zone , becomes more probable. The development of Legionella spp. and Aeromonas spp. could be inhibited by competition with other microorganisms like nonpathogenic species of aquatic bacteria. Interactions between these groups of microorganisms depending on the physico-chemical condition of water from lakes of different trophic status are still not fully elucidated.We will analyse the relationship between the phylogenetic and physiological structure of bacterial community and the occurrence of pathogenic bacteria belonging to genus Legionella and Aeromonas, including the especially dangerous Legionella pneumophila and Aeromonas hydrophila species, in lakes of differing trophic status. Moreover, we will study the influence of short-term temperature increases on the share of these pathogens in the total lake bacteria biomass. The following main hypotheses will be verified: 1) There is a close relationship between the trophic status of lakes and Legionella spp. and Aeromonas spp. occurrence. 2) There is close relationship between the quantified occurrence of Legionella spp. and Aeromonas spp. and the phylogenetic and physiological (metabolic finger print) characteristics of the microbial community coexisting with these pathogens. 3) Short-term water temperature increases may lead to significant increases of Legionella spp. and Aeromonas spp. share in the total number of bacteria inhabiting lake water.