Chapters authored
Grazing Effects of Ciliates on Microcolony Formation in Bacterial Biofilms
The attachment to surfaces and the subsequent formation of biofilms are a life strategy of bacteria offering several advantages for microorganisms, for example, a protection against toxins and antibiotics and profits due to synergistic effects in biofilm environment. Moreover, biofilm formation is thought to serve as grazing protection against predators. From pelagic systems it is known that feeding of bacterivorous protists may strongly influence the morphology, taxonomic composition and physiological status of bacterial communities and thus may be an important driving force for a change in bacterial growth and shift in morphology towards filaments and flocs. Bacteria in biofilms had to evolve several other defence strategies: production of extrapolymeric substances (EPS) or toxins, formation of specific growth forms with strong attachment, specific chemical surface properties and motility. In addition, bacteria can communicate via quorum sensing and react on grazing pressure. The results of the case study presented here showed that even microcolonies in bacterial biofilms are affected by the activity of grazers, though it may depend on the nutrient supply. Feedback effects due to remineralization of nutrients because of intensive grazing may stimulate biofilm growth and thereby enhancing grazing defence. Predator effects might be much more complex than they are currently believed to be.
Part of the book: Microbial Biofilms