title: Loss of topoisomerase I function affects the RpoS-dependent and GAD systems of acid resistance in Escherichia coli.
abstract: Acid resistance (AR) in Escherichia coli is important for its survival in the human gastrointestinal tract and involves three systems. The first AR system is dependent on the sigma factor RpoS. The second system (the GAD system) requires the glutamate decarboxylase isoforms encoded by the gadA and gadB genes. The third system (the ARG system) requires the arginine decarboxylase encoded by adiA. Loss of topoisomerase I function from topA deletion or Tn10 insertion mutations lowered the resistance to killing by pH 2 or 2.5 treatment by 10-fold to >100-fold. The RpoS and GAD systems were both affected by the topA mutation, but the ARG system of AR was not affected. Northern blot analysis showed that induction of gadA and gadB transcription in stationary phase and at pH 5.5 was decreased in the topA mutant. Western blot analysis showed that the topA mutation did not affect accumulation of RpoS, GadX or GadW proteins. Topoisomerase I might have a direct influence on the transcription of AR genes. This influence does not involve R-loop formation as the overexpression of RNase H did not alleviate the decrease of AR caused by the topA mutation. The effect of the topA mutation could be suppressed by an hns mutation, so topoisomerase I might be required to counteract the effect of H-NS protein on gene expression, in addition to its influence on RpoS-dependent transcription.
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Natalee
authors.initials: N
authors.lastname: Stewart
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Jingyang
authors.initials: J
authors.lastname: Feng
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Devyani
authors.initials: D
authors.lastname: Chaudhuri
authors.affiliation: Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile, AL 36688, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Foster
authors.affiliation: Départment de Microbiologie et Immunologie, Université de Montréal, CP 6128, Succursale Centre-ville, Montréal, P. Québec, Canada H3C 3J7.
authors.forename: Marc
authors.initials: M
authors.lastname: Drolet
authors.affiliation: Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
authors.forename: Yuk-Ching
authors.initials: YC
authors.lastname: Tse-Dinh
mesh_terms: D000143:Acids / Q000378:metabolism / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000502:physiology*; D004264:DNA Topoisomerases, Type I / Q000172:deficiency*; D004352:Drug Resistance, Microbial / Q000502:physiology*; D004926:Escherichia coli / Q000201:enzymology / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D000143:Acids; D001426:Bacterial Proteins; D005227:Fatty Acids; C103589:GadC protein, bacteria; D008565:Membrane Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D004264:DNA Topoisomerases, Type I