PREDATION ON THE MICROSCALE – BACTERIAL PREDATORS DYNAMICS AND INTERACTIONS IN WATER TREATMENT PLANTS

Predation is a well-studied major mode of interaction between organisms but its contribution to the ecology of microbial populations is only emerging. In the marine habitat, the impact of predation upon bacteria and the resulting mortality are important mechanisms in controlling bacterial populations and in the recycling of nutrients through the microbial loop. The most investigated micropredators responsible for bacterial mortality are viruses and protists. However, predatory bacteria are yet another group of micropredators that may affect microbial populations. Here we used Bdellovibrio and like organisms (BALOs) to assess the impact of predation between bacteria and the environmental parameters controlling it. To that aim, microbial populations and their dynamics were characterized in three wastewater treatment plants (WWTPs) located in Germany, in Israel, in the Palestinian Authority, as well as in a polluted, untreated environment (the Kidron stream). The overall bacterial community, BALOs, and protists were sampled during the course of 12 months chemical and physical data collected. High throughput sequencing combined with qPCR revealed diverse and dynamic populations of in the Bdellovibrionaceae and Bacteriovoracaceae families of predators, accounting for 0.5 to 1% of the total bacterial population. The predatory populations differed and oscillated differently between the sampled environments. A distinct bio geographic difference in bacterial predators abundance and population dynamics was revealed between the water treated environments to the untreated environment. Correlations between predatory and the total microbial population reveals specific connections between the abundance of several bacterial predators with specific bacterial families.