title: Internal pH crisis, lysine decarboxylase and the acid tolerance response of Salmonella typhimurium.
abstract: Salmonella typhimurium possesses an adaptive response to acid that increases survival during exposure to extremely low pH values. The acid tolerance response (ATR) includes both log-phase and stationary-phase systems. The log-phase ATR appears to require two components for maximum acid tolerance, namely an inducible pH homeostasis system, and a series of acid-shock proteins. We have discovered one of what appears to be a series of inducible exigency pH homeostasis systems that contribute to acid tolerance in extreme acid environments. The low pH-inducible lysine decarboxylase was shown to contribute significantly to pH homeostasis in environments as low as pH 3.0. Under the conditions tested, both lysine decarboxylase and sigma s-dependent acid-shock proteins were required for acid tolerance but only lysine decarboxylase contributed to pH homeostasis. The cadBA operon encoding lysine decarboxylase and a lysine/cadaverine antiporter were cloned from S. typhimurium and were found to be 79% homologous to the cadBA operon from Escherichia coli. The results suggest that S. typhimurium has a variety of means of fulfilling the pH homeostasis requirement of the ATR in the form of inducible amino acid decarboxylases.
authors: Department of Biology, Korea University, Soeul, Korea.
authors: Y K
authors: YK
authors: Park
authors: B
authors: B
authors: Bearson
authors: S H
authors: SH
authors: Bang
authors: I S
authors: IS
authors: Bang
authors: J W
authors: JW
authors: Foster
mesh_terms: D000143:Acids; D001483:Base Sequence; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009876:Operon; D012486:Salmonella typhimurium / Q000201:enzymology / Q000502:physiology*; D017422:Sequence Analysis, DNA
chemical_list: D000143:Acids; D004269:DNA, Bacterial; D002262:Carboxy-Lyases; C021520:lysine decarboxylase