Bacterial and protists diversity/dynamics study in bulk water of cooling towers by barcoded amplicon approach.

Cooling towers are provides suitable environments for microbial growth and are known sources of human disease outbreaks, e.g. Legionnaire's disease. In addition, the presence of protists in cooling towers has also been reported. Protists like Free-Living-Amoebae (FLA) are known hosts of human pathogens, increasing their pathogenesis and providing shelter from environmental harm. However although efforts has been made to minimize the likelihood of an outbreak by regular screening for known human pathogens, the general microbial- and protist-diversity as well as their dynamics remains elusive. Here we sampled the bulk water of three cooling towers over the course of 1 year on a biweekly basis and sequenced the partial 16S and 18S rRNA by a barcoded-amplicon sequencing approach. Each location exhibit their unique bacterial and protist diversity but are comparable to other known freshwater systems. Further, the core taxa consists of groups usually associated with biofilm formation. Although the cooling towers provide a rather stable environment, the microbial communities are dynamic and subjected to seasonal change. We detected the presence of members of groups including putative pathogens. The co-occurrence analysis were able to recaptured known interaction between amoeba-associated endosymbionts and protists. This paper provides the first overview of microbial diversities and their potential interactions in this man-made aquatic system and serves as a basis for future studies.