Fig. 7.

Site-specific and shared protist OTUs in three cooling towers. The Venn diagram in (A) represents the proportion of shared and site-specific protist OTUs at the three sampling sites. In contrast to the less variable bacterial community composition, the majority of the protist OTUs are site-specific, and the number of OTUs shared by all three sampling sites constitutes only a very small fraction of all OTUs. (B) The heat tree indicates the taxonomic classification of the six shared OTUs, most of which are free-living amoebae (Hartmannella, Vexillifera, Stenamoeba). Unclassified taxa are unlabeled.