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Journal of Bacteriology, December 2004, p. 8096-8104, Vol. 186, No. 23
0021-9193/04/$08.00+0 DOI: 10.1128/JB.186.23.8096-8104.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
and
Alfred M. Spormann1,2,3*
Departments of Civil and Environmental Engineering,1 Biological Sciences,2 Geological and Environmental Sciences, Stanford University, Stanford, California3
Received 10 April 2004/ Accepted 24 August 2004
Shewanella oneidensis MR-1 is a facultative Fe(III)- and Mn(IV)-reducing microorganism and serves as a model for studying microbially induced dissolution of Fe or Mn oxide minerals as well as biogeochemical cycles. In soil and sediment environments, S. oneidensis biofilms form on mineral surfaces and are critical for mediating the metabolic interaction between this microbe and insoluble metal oxide phases. In order to develop an understanding of the molecular basis of biofilm formation, we investigated S. oneidensis biofilms developing on glass surfaces in a hydrodynamic flow chamber system. After initial attachment, growth of microcolonies and lateral spreading of biofilm cells on the surface occurred simultaneously within the first 24 h. Once surface coverage was almost complete, biofilm development proceeded with extensive vertical growth, resulting in formation of towering structures giving rise to pronounced three-dimensional architecture. Biofilm development was found to be dependent on the nutrient conditions, suggesting a metabolic control. In global transposon mutagenesis, 173 insertion mutants out of 15,000 mutants screened were identified carrying defects in initial attachment and/or early stages in biofilm formation. Seventy-one of those mutants exhibited a nonswimming phenotype, suggesting a role of swimming motility or motility elements in biofilm formation. Disruption mutations in motility genes (flhB, fliK, and pomA), however, did not affect initial attachment but affected progression of biofilm development into pronounced three-dimensional architecture. In contrast, mutants defective in mannose-sensitive hemagglutinin type IV pilus biosynthesis and in pilus retraction (pilT) showed severe defects in adhesion to abiotic surfaces and biofilm formation, respectively. The results provide a basis for understanding microbe-mineral interactions in natural environments.
Present address: Oak Ridge National Laboratory, Oak Ridge, TN 37831-6149.
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