Protozoan grazing and its impact upon population dynamics in biofilm communities

Aims: To determine the impact of protozoan grazing on the population dynamics of a multispecies bacterial biofilm community. Methods and Results: Grazing by Acanthamoeba castellanii and the ciliate Colpoda maupasi upon biofilm and planktonic communities, composed of Klebsiella pneumoniae, Pseudomonas fluorescens and Staphylococcus epidermidis was investigated. Biofilms were formed using glass coverslips, held in a carousel device, as substrata for biofilm formation or in glass flow cells. The predatory effects of the amoeba were generally confined to the biofilm, where grazing rates corresponded to losses from the biofilm equivalent to ca 30 000 biofilm cells cm -2h-1, with the amoeba becoming an integral part of the community. C. maupasi reduced the thickness of mature multispecies biofilms at steady-state from 500 to