John Kirby Laboratory

  • Research

    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.

    Chemosensory regulation of Motility, Physiology & Development in M. xanthus

    Chemosensory regulation in bacteria

    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.

    Mechanism of Chemotaxis in Bacillus subtilis

    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.