This proposal investigates the responses of the model Gram positive bacterium Bacillus subtilis to metal ion starvation. When cells are starved for essential metals, such as iron or zinc, they express complex adaptive responses. These responses include the elaboration of high affinity uptake systems to obtain metals from the environment. Perhaps even more important, cells reprogram their metabolism to block the synthesis of unneeded proteins and enzymes that will consume the limiting nutrient. In the case of iron, this "iron-sparing response" leads to large scale changes in the protein composition and metabolic potential of the cell and has wide-ranging ramifications for cell physiology. Iron-sparing responses have evolved multiple times in various organisms and are mediated by a variety of RNA- and protein-based regulators. In B. subtilis, the iron-sparing response requires a regulatory, small RNA that functions in collaboration with three genes encoding small, basic peptides. These small proteins are postulated to function, at least in part, as RNA chaperones. Preliminary results suggest that the response to zinc starvation is also complex and multifaceted. Repression of the synthesis of non-essential zinc metalloproteins provides a "zinc-sparing response" and the expression of a set of alternative ribosomal proteins displaces small, Zn-containing peptides from the ribosome to provide zinc for the cell. In addition to the expression of high affinity metal ion uptake (acquisition) and the repression of non-essential metalloproteins (sparing), cells also express alternative isozymes for some essential functions that might otherwise be compromised (substitution). This proposal will focus on the characterization of these and related adaptive responses that enable cells to compete effectively even in severely metal-limited environments.

Public Health Relevance

Project Narrative Metal ions are essential for life and function as cofactors for numerous enzymatic and electron transfer processes. This proposal seeks to understand how the model Gram positive bacterium Bacillus subtilis adapts to limitation for iron and zinc. These studies will provide significant insights into the adaptive processes which enable Gram positive pathogens (e.g. Staphylococcus aureus, streptococci, and enterococci) to survive in the metal-limited environments encountered in the host.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IDM-Q (03))
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Chin, Jean
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Cornell University
Schools of Earth Sciences/Natur
United States
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Helmann, John D (2014) Specificity of metal sensing: iron and manganese homeostasis in Bacillus subtilis. J Biol Chem 289:28112-20
Chandrangsu, Pete; Dusi, Renata; Hamilton, Chris J et al. (2014) Methylglyoxal resistance in Bacillus subtilis: contributions of bacillithiol-dependent and independent pathways. Mol Microbiol 91:706-15
Ma, Zhen; Chandrangsu, Pete; Helmann, Tyler C et al. (2014) Bacillithiol is a major buffer of the labile zinc pool in Bacillus subtilis. Mol Microbiol 94:756-70
McGuire, Amanda M; Cuthbert, Bonnie J; Ma, Zhen et al. (2013) Roles of the A and C sites in the manganese-specific activation of MntR. Biochemistry 52:701-13
Smaldone, Gregory T; Antelmann, Haike; Gaballa, Ahmed et al. (2012) The FsrA sRNA and FbpB protein mediate the iron-dependent induction of the Bacillus subtilis lutABC iron-sulfur-containing oxidases. J Bacteriol 194:2586-93
Smaldone, Gregory T; Revelles, Olga; Gaballa, Ahmed et al. (2012) A global investigation of the Bacillus subtilis iron-sparing response identifies major changes in metabolism. J Bacteriol 194:2594-605
Faulkner, Melinda J; Ma, Zhen; Fuangthong, Mayuree et al. (2012) Derepression of the Bacillus subtilis PerR peroxide stress response leads to iron deficiency. J Bacteriol 194:1226-35
Gaballa, Ahmed; MacLellan, Shawn; Helmann, John D (2012) Transcription activation by the siderophore sensor Btr is mediated by ligand-dependent stimulation of promoter clearance. Nucleic Acids Res 40:3585-95
Ma, Zhen; Lee, Jin-Won; Helmann, John D (2011) Identification of altered function alleles that affect Bacillus subtilis PerR metal ion selectivity. Nucleic Acids Res 39:5036-44
Faulkner, Melinda J; Helmann, John D (2011) Peroxide stress elicits adaptive changes in bacterial metal ion homeostasis. Antioxid Redox Signal 15:175-89

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