Affiliation:
1. Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
Abstract
ABSTRACT
The extracellular matrix fibrils of
Myxococcus xanthus
are essential for the social lifestyle of this unusual bacterium. These fibrils form networks linking or encasing cells and are tightly correlated with cellular cohesion, development, and social (S) gliding motility. Previous studies identified a set of bacterial chemotaxis homologs encoded by the
dif
locus. It was determined that
difA
,
difC
, and
difE
, encoding respective homologs of a methyl-accepting chemotaxis protein, CheW, and CheA, are required for fibril production and therefore S motility and development. Here we report the studies of three additional genes residing at the
dif
locus,
difB
,
difD
, and
difG. difD
and
difG
encode homologs of chemotaxis proteins CheY and CheC, respectively.
difB
encodes a positively charged protein with limited homology at its N terminus to conserved bacterial proteins with unknown functions. Unlike the previously characterized
dif
genes, none of these three newly studied
dif
genes are essential for fibril production, S motility, or development. The
difB
mutant showed no obvious defects in any of the processes examined. In contrast, the
difD
and the
difG
mutants were observed to overproduce fibril polysaccharides in comparison with production by the wild type. The observation that DifD and DifG negatively regulate fibril polysaccharide production strengthens our hypothesis that the
M. xanthus dif
genes define a chemotaxis-like signal transduction pathway which regulates fibril biogenesis. To our knowledge, this is the first report of functional studies of a CheC homolog in proteobacteria. In addition, during this study, we slightly modified previously developed assays to easily quantify fibril polysaccharide production in
M. xanthus
.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
102 articles.
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