The HTH domain may contribute to this process by interacting
with various protein molecules and localizing RodZ itself into the membrane. For these reasons, a higher expression of RodZΔHTH than the intact RodZ might have been required to complement defects caused by the ΔrodZ mutation. Nonetheless, RodZ was not absolutely required for the rod shape. We isolated pseudorevertants of the ΔrodZ mutant (KR0401ΔrodZ-mot+). They possessed a rod shape, although cells Bioactive Compound high throughput screening were irregular and not well balanced as the wild type. It was reported that RodZ interacts with and anchor MreB to the inner membrane, promoting the helical assembly of actin cytoskeleton (Bendezúet al., 2009; van den Ent et al., 2010). We speculate that the function of RodZ in the lateral synthesis of the cell wall was somehow compensated in the pseudorevertants, although the proper assembly of MreB was still lost due to the absence of RodZ and consequently the rigid rod shape was not maintained. Because rodZ is an essential gene in Caulobacter (Alyahya et al., 2009), E. coli might
have another gene or mechanism that can complement the loss of rodZ. Genome-wide differential gene expression analysis of the ΔrodZ-mot+ derivative will be interesting and important to elucidate the FDA approved Drug Library cell assay function of rodZ in relation to cell morphogenesis. We thank Drs Gottfried Unden (Johannes Gutenberg Universität Mainz, Germany) and John Cronan (University of Illinois, USA) for providing us with plasmids and Dr Francis Bivelle (Institut Pasteur, France) for λInCh. We are grateful to Dr Toshinobu Suzaki (Kobe University, Japan) and members of his laboratory for kindly providing TEM facilities and helping us in electron microscopic
analysis. We also thank Dr Katsumi Isono of the Kazusa DNA Research Institute for his critical reading of the manuscript. “
“Functional genes required for microbial (dissimilatory) metal reduction display high sequence divergence, which limits their utility as molecular biomarkers for tracking the presence and activity of metal-reducing bacteria in natural and engineered systems. In the present study, homologs of the outer membrane beta-barrel protein MtrB of metal-reducing Gammaproteobacteria were found to contain a unique N-terminal CXXC motif that was missing from MtrB homologs of PJ34 HCl nonmetal-reducing Gammaproteobacteria and metal- and nonmetal-reducing bacteria outside the Gammaproteobacteria. To determine whether the N-terminal CXXC motif of MtrB was required for dissimilatory metal reduction, each cysteine in the CXXC motif of the representative metal-reducing gammaproteobacterium Shewanella oneidensis was replaced with alanine, and the resulting site-directed mutants were tested for metal reduction activity. Anaerobic growth experiments demonstrated that the first, but not the second, conserved cysteine was required for metal reduction by S. oneidensis.