title: Glutamate dehydrogenase affects resistance to cell wall antibiotics in Bacillus subtilis.
abstract: The glutamate dehydrogenase RocG of Bacillus subtilis is a bifunctional protein with both enzymatic and regulatory functions. Here we show that the rocG null mutant is sensitive to β-lactams, including cefuroxime (CEF), and to fosfomycin but that resistant mutants arise due to gain-of-function mutations in gudB, which encodes an otherwise inactive glutamate dehydrogenase. In the presence of CEF, ΔrocG ΔgudB mutant cells exhibit growth arrest when they reach mid-exponential phase. Using microarray-based transcriptional profiling, we found that the σ(W) regulon was downregulated in the ΔrocG ΔgudB null mutant. A survey of σ(W)-controlled genes for effects on CEF resistance identified both the NfeD protein YuaF and the flotillin homologue YuaG (FloT). Notably, overexpression of yuaFG in the rocG null mutant prevents the growth arrest induced by CEF. The YuaG flotillin has been shown previously to localize to defined lipid microdomains, and we show here that the yuaFGI operon contributes to a σ(W)-dependent decrease in membrane fluidity. We conclude that glutamate dehydrogenase activity affects the expression of the σ(W) regulon, by pathways that are yet unclear, and thereby influences resistance to CEF and other antibiotics.
authors.affiliation: Department of Microbiology, Cornell University, Ithaca, New York, USA.
authors.forename: Yong Heon
authors.initials: YH
authors.lastname: Lee
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Kingston
authors.forename: John D
authors.initials: JD
authors.lastname: Helmann
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects* / Q000201:enzymology* / Q000254:growth & development; D001426:Bacterial Proteins / Q000378:metabolism*; D002444:Cefuroxime / Q000494:pharmacology; D002473:Cell Wall / Q000187:drug effects*; D024881:Drug Resistance, Bacterial; D005578:Fosfomycin / Q000494:pharmacology; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005969:Glutamate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D046228:Microarray Analysis; D018085:Regulon; D012808:Sigma Factor / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C413458:SigW protein, Bacillus subtilis; D012808:Sigma Factor; D005578:Fosfomycin; D005969:Glutamate Dehydrogenase; D002444:Cefuroxime