Anaerobic Gene Regulation in Bacillus Subtilis

Oregon Health & Science University, Portland OR

Investigators

Abstract

Bacillus subtilis is able to respire with either oxygen (aerobic respiration) or nitrate (anaerobic respiration). Both forms of respiration require the ResD-ResE two-component signal transduction system. ResD, phosphorylated by ResE sensor kinase, activates transcription of genes required for aerobic and anaerobic respiration. This project will uncover the regulatory mechanisms by which B. subtilis commits to undergo anaerobic respiration. Two regulatory proteins NsrR and unphosphorylated ResD play critical roles in the decision-making process. NsrR is a Fe-S transcription regulator that represses anaerobic respiration genes but the repressor activity is eliminated in response to nitric oxide (NO) produced during nitrate respiration. This research determines how NO modifies the Fe-S cluster in NsrR and how this modification alters NsrR activity. Unphosphorylated ResD activates anaerobic respiration genes in response to oxygen limitation. Two hypotheses will be tested: One, that ResD itself activates transcription or, two, that an accessory factor interacting with ResD and/or the promoter DNA is responsible for transcriptional activation. To investigate these possibilities, mutations that affect unphosphorylated ResD-dependent activation will be isolated and characterized. The responses of microorganisms to oxygen limitation and to NO greatly impact the activities involved in the earth's nitrogen cycles and in pathogenesis. Both NsrR and two-component signal transduction proteins are widely present in bacteria. The research takes advantage of a powerful bacterial genetic system and leading-edge metallobiochemistry to gain new insights into these ubiquitous regulators and their associated mechanisms. Broader impact of this project is multidisciplinary research training in bioinorganic chemistry and molecular genetics for a variety of groups. These diverse groups include not only Ph.D. students but also non-thesis M.S. students who, after completing one-year training in scientific research and education, continue their careers in graduate school (Ph.D.), medical school, or as research technicians in both academic and industrial laboratories. The project will also train undergraduates supported by summer internship opportunities offered by the department and REU supplement funds, high school students supported through Saturday Academy, and high school teachers supported by Partners in Science Program of M.J. Murdock Charitable Trust, in which the P.I. has participated.