This proposal investigates cell envelope stress responses in Bacillus subtilis, a model organism for the Gram positive bacteria. Antibiotics and other agents that impair the synthesis or function of the cell membrane or peptidoglycan cell wall are of critical importance in clinical medicine. Exposure to sub-lethal levels of antibiotics activates the transcription of sets of genes (cell envelope stress responses) that serve to remodel the cell wall and membrane. In B. subtilis, these stress responses are coordinated by alternative sigma subunits for RNA polymerase of the extracytoplasmic function (ECF) subfamily. This proposal is focused on defining the role of ECF sigma factors in controlling adaptive changes in cell envelope function. One focus will be on the roles of induced lipid biosynthesis pathways and proteins in the genesis and function of lipid rafts. A second focus will be to discover the roles of a newly defined second messenger, cyclic-di-AMP, that is required for cell envelope homeostasis. Using a combination of classical and molecular genetics, genomics, transcriptomics, and biochemical approaches, these studies will provide insights into cell envelope synthesis and function, and reveal novel mechanisms of antibiotic resistance.

Public Health Relevance

The bacterial envelope, comprising a lipid membrane and a peptidoglycan cell wall, separates the cell from the environment and is a target for the majority of antibiotics currently in clinical use. This proposal identifies pathways by which bacteria respond to antibiotic threats by modifying the biosynthesis of the cell envelope with implications for the development of antibiotic resistance. This proposal focuses specifically on the model Gram positive bacterium Bacillus subtilis which is related to Staphylococcus aureus and pathogenic streptococcal and enterococcal strains.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Prokaryotic Cell and Molecular Biology Study Section (PCMB)
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Reddy, Michael K
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Cornell University
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United States
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Cai, Yanfei; Chandrangsu, Pete; Gaballa, Ahmed et al. (2017) Lack of formylated methionyl-tRNA has pleiotropic effects on Bacillus subtilis. Microbiology 163:185-196
Xue, Xiaowei; Davis, Maria C; Steeves, Thomas et al. (2016) Characterization of a protein-protein interaction within the SigO-RsoA two-subunit ? factor: the ?70 region 2.3-like segment of RsoA mediates interaction with SigO. Microbiology 162:1857-1869
Helmann, John D (2016) Bacillus subtilis extracytoplasmic function (ECF) sigma factors and defense of the cell envelope. Curr Opin Microbiol 30:122-132
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Helmann, John D (2015) Chemical proteomics reveals a second family of cyclic-di-AMP hydrolases. Proc Natl Acad Sci U S A 112:1921-2
Kashyap, Des Raj; Rompca, Annemarie; Gaballa, Ahmed et al. (2014) Peptidoglycan recognition proteins kill bacteria by inducing oxidative, thiol, and metal stress. PLoS Pathog 10:e1004280
Gaballa, Ahmed; Chi, Bui Khanh; Roberts, Alexandra A et al. (2014) Redox regulation in Bacillus subtilis: The bacilliredoxins BrxA(YphP) and BrxB(YqiW) function in de-bacillithiolation of S-bacillithiolated OhrR and MetE. Antioxid Redox Signal 21:357-67
Lee, Yong Heon; Helmann, John D (2014) Mutations in the primary sigma factor ?A and termination factor rho that reduce susceptibility to cell wall antibiotics. J Bacteriol 196:3700-11

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