Author: Jana Mueller

Publisher: Stanford University

Published: 2010

Total Pages: 166

ISBN-13:

S. oneidensis MR-1 is a dissimilatory metal-reducing bacterium. Under anaerobic conditions S. oneidensis MR-1 attaches to insoluble minerals such as Fe(III) and Mn(IV) oxides and can use these as alternative electron acceptors. Biofilms of S. oneidensis MR- 1 were previously found to be dependent on the mxd gene cluster (mxdABCD). This study identified environmental and genetic factors regulating mxd -dependent and -independent biofilm formation in S. oneidensis MR-1 and a putative function for mxdB in LPS biosynthesis. Physiological experiments determined electron donor starvation as a factor responsible for mxd induction. Tn5 mutagenesis identified the two-component signaling system (TCS) ArcS/ArcA and a putative TCS BarA/UvrY as regulators of mxd expression. ccmC, important for cytochrome c maturation, was found to be involved in biofilm formation in S. oneidensis MR-1. Microarray analysis identified ccmC to play a role in aspects of anaerobic and fermentative metabolism in S. oneidensis MR-1. In conclusion, these data indicate a potential connection between energy metabolism of the cell, mxd and biofilm formation in S. oneidenis MR-1. The natural life cycle of the phylogenetically closest relative V. cholerae A1552 involves the transitioning of cells between different environmental surfaces such as the chitinous shell of Crustaceae and the epithelial layer of the human intestine and vice versa. Biofilms of V. cholerae A1552 vpsA and luxO mutants grown under hydrodynamic flow conditions were found to form pronounced, three-dimensional biofilms that resemble all aspects of wild type biofilms. By genetic experiments, it was shown that in hydrodynamically-grown biofilms this independence of vpsA is due to the expression of rpoS, which is a negative regulator of vpsA expression. Biofilms also underwent substantial metabolically controlled dissolution after 96 h that could be induced by a simple stop of medium flow across the biofilm. These studies indicate that metabolic conditions control the reversible attachment of cells to the biofilm matrix and are key in regulating biofilm cell physiology via rpoS. Furthermore, these results redefine the roles of vps and quorum-sensing in V. cholerae A1552 biofilms.