Present address: Federal Institute of Hydrology, Department of Ecological Interactions, 56002 Koblenz, Germany.
Microcolonies, quorum sensing and cytotoxicity determine the survival of Pseudomonas aeruginosa biofilms exposed to protozoan grazing
Article first published online: 29 JAN 2004
Volume 6, Issue 3, pages 218–226, March 2004
How to Cite
Matz, C., Bergfeld, T., Rice, S. A. and Kjelleberg, S. (2004), Microcolonies, quorum sensing and cytotoxicity determine the survival of Pseudomonas aeruginosa biofilms exposed to protozoan grazing. Environmental Microbiology, 6: 218–226. doi: 10.1111/j.1462-2920.2004.00556.x
- Issue published online: 29 JAN 2004
- Article first published online: 29 JAN 2004
- Received 27 August, 2003; accepted 29 October, 2003.
This study was based on the hypothesis that biofilms of the opportunistic pathogen Pseudomonas aeruginosa are successfully adapted to situations of protozoan grazing. We tested P. aeruginosa wild type and strains that were genetically altered, in structural and regulatory features of biofilm development, in response to the common surface-feeding flagellate Rhynchomonas nasuta. Early biofilms of the wild type showed the formation of grazing resistant microcolonies in the presence of the flagellate, whereas biofilms without the predator were undifferentiated. Grazing on biofilms of quorum sensing mutants (lasR and rhlR/lasR) also resulted in the formation of microcolonies, however, in lower numbers and size compared to the wild type. Considerably fewer microcolonies than the wild type were formed by mutant cells lacking type IV pili, whereas no microcolonies were formed by flagella-deficient cells. The alginate-overproducing strain PDO300 developed larger microcolonies in response to grazing. These observations suggest a role of quorum sensing in early biofilms and involvement of flagella, type IV pili, and alginate in microcolony formation in the presence of grazing. More mature biofilms of the wild type exhibited acute toxicity to the flagellate R. nasuta. Rapid growth of the flagellate on rhlR/lasR mutant biofilms indicated a key role of quorum sensing in the upregulation of lethal factors and in grazing protection of late biofilms. Both the formation of microcolonies and the production of toxins are effective mechanisms that may allow P. aeruginosa biofilms to resist protozoan grazing and to persist in the environment.