The acid tolerance response of Salmonella typhimurium provides protection against organic acids

• Published in: Microbiology (Society for General Microbiology) 1996-11, Vol.142 (11), p.3195-3200
• Main Authors: Baik, Hyung Suk, Bearson, Shawn, Dunbar, Sherry, Foster, John W
• Format: Article
• Language: English
• Subjects: Acids - pharmacology; Action of physical and chemical agents on bacteria; Bacteriology; Biological and medical sciences; Chromosome Mapping; Culture Media; Drug Resistance, Microbial - genetics; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; Hydrogen-Ion Concentration; Microbiology; Mutation; Salmonella typhimurium - drug effects; Salmonella typhimurium - genetics; Salmonella typhimurium - growth & development
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/13500872-142-11-3195

Department of Microbiology and Immunology, University of South Alabama, College of Medicine, Mobile, AL 36688, USA ABSTRACT Salmonella typhimurium encounters a variety of acid stress situations during pathogenesis and in the natural environment. These include the extreme low pH encountered in the stomach and a less acidic intestinal environment containing large amounts of organic weak acids (volatile fatty acids). The acid tolerance response (ATR) is a complex defence system that can minimize the lethal effects of extreme low pH (pH 3). The data presented illustrate that the ATR can also defend against weak acids such as butyric, acetic or propionic acids. Although an acid shock of pH 4.4 induced the ATR, growth in subinhibitory concentrations of weak acids did not. Various mutations shown to affect tolerance to extreme acid conditions (pH 3) were tested for their effects on tolerance to weak acids. An rpoS mutant lacking the alternative sigma factor s S failed to protect cells against weak acids as well as extreme acid pH. The fur (ferric uptake regulator) and atp (Mg 2+ -dependent ATPase) mutants defective in extreme acid tolerance showed no defects in their tolerance to weak acids. Curiously, the atbR mutant that exhibits increased tolerance to extreme acid pH proved sensitive to weak acids. Several insertions that rendered cells sensitive to organic acids were isolated, all of which proved to be linked to the rpoS locus. 1 Author for correspondence: John W. Foster. Tel: [phone]. Fax: [phone]. e-mail: [e-mail] Keywords: Salmonella typhimurium , acid tolerance, s S , RpoS, volatile fatty acids Present address: Veterans Affairs Medical Center, Department of Pathology and Laboratory Medicine-113, 2002 Holcombe Blvd, Houston, TX 77030, USA. Present address: Department of Microbiology, College of Natural Sciences, Pusan National University, Pusan 609-735, Korea.