Microcolonies, quorum sensing and cytotoxicity determine the survival of Pseudomonas aeruginosa biofilms exposed to protozoan grazing
- 29 January 2004
- journal article
- Published by Wiley in Environmental Microbiology
- Vol. 6 (3), 218-226
- https://doi.org/10.1111/j.1462-2920.2004.00556.x
Abstract
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.Keywords
This publication has 38 references indexed in Scilit:
- Effects of nutrient availability and Ochromonas sp. predation on size and composition of a simplified aquatic bacterial communityFEMS Microbiology Ecology, 2006
- Biofilm formation by Pseudomonas aeruginosa wild type, flagella and type IV pili mutantsMolecular Microbiology, 2003
- Negative Control of Quorum Sensing by RpoN (σ54) inPseudomonas aeruginosaPAO1Journal of Bacteriology, 2003
- The alternative sigma factor RpoN regulates the quorum sensing generhlIinPseudomonas aeruginosaFEMS Microbiology Letters, 2003
- Phenotypic variation in Pseudomonas sp. CM10 determines microcolony formation and survival under protozoan grazingFEMS Microbiology Ecology, 2002
- Differential Roles of the Pseudomonas aeruginosa PA14 rpoN Gene in Pathogenicity in Plants, Nematodes, Insects, and MiceJournal of Bacteriology, 2001
- Grazing of protozoa and its effect on populations of aquatic bacteriaFEMS Microbiology Ecology, 2001
- Mucoid conversion of Pseudomonas aeruginos by hydrogen peroxide: a mechanism for virulence activation in the cystic fibrosis lungMicrobiology, 1999
- Feeding behaviour and grazing impacts of a Euplotes sp. on attached bacteriaCanadian Journal of Microbiology, 1998
- MICROBIAL BIOFILMSAnnual Review of Microbiology, 1995