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We are interested in chemosensory signal transduction systems that
regulate motility and development in the bacterial model organisms, Myxococcus xanthus and Bacillus subtilis.
Chemosensory systems are chemotaxis-like two component systems that
regulate a variety of cellular functions ranging from flagellar based
motility to sporulation.
Analysis of signal transduction systems that allow cells to detect and
mediate responses to environmental factors, including neighbor contact,
is the major subject of investigation in our lab. M. xanthus is
a soil bacterium that displays a multicellular life cycle. Cells feed
on other organisms and form complex fruiting structures, culminating in
spore production when starved. These processes require Type IV
pilus-based motility and depend on chemotaxis and complex intercellular
signaling. M. xanthus utilizes over 120 two-component systems,
including eight homologous chemosensory signaling pathways to regulate
its complex lifestyle. While some of these che homologs are involved in
the regulation of motility and predation, others have been shown to
affect a variety of cellular functions including gene expression and
carotenoid biosynthesis. Our projects focus on the chemosensory
regulation of gene expression, lipoprotein-dependent stress responses,
type IV pilus assembly, and membrane composition.
Analysis of the B. subtilis chemotaxis system focuses our work on CheC, CheD, and CheV. Homologs to these proteins are not found in E. coli
but are present in the majority of known chemotactic Bacteria and
Archaea. Our projects include the characterization of CheD deamidase
activity and HAMP domain interactions, targets and regulation of CheC
phosphatase activity, and regulation of signaling by the unique
receptor-kinase coupling protein, CheV. The broad distribution of CheC,
CheD and CheV identified by genome sequencing allows us to conclude that
B. subtilis is the best paradigm for the study of chemotaxis in prokaryotes.