Lysine decarboxylase of Vibrio parahaemolyticus: kinetics of transcription and role in acid resistance.
OBJECTIVE
The aim of this study was to investigate the detailed mechanisms of acid resistance in Vibrio parahaemolyticus.


RESULTS
All 11 strains of V. parahaemolyticus survived lethal acidic conditions following acid adaptation, and accumulation of cadaverine was detected. The addition of lysine improved survival, suggesting that lysine decarboxylase plays a role in the adaptive acid tolerance response. Two open reading frames (ORF) in V. parahaemolyticus, which are separated by a noncoding region, were found to be highly homologous to bacterial lysine decarboxylase (cadA) and lysine/cadaverine antiporter (cadB) genes. Transcriptional analyses of this operon revealed acid induction and enhanced induction by external lysine. The relative expression ratio of each transcript was found to follow the trend of cadA mRNA > cadB mRNA > cadBA bi-cistronic mRNA. A mutated strain, with a disrupted cadA gene, showed attenuated acid survival.


CONCLUSIONS
We identified the lysine decarboxylase gene operon of V. parahaemolyticus. Expression of this operon was induced under acidic conditions. The cadA-mutated strain constructed in this study showed weaker tolerance to acidic conditions than the wild-type strain.


CONCLUSIONS
Vibrio parahaemolyticus utilizes the lysine decarboxylation pathway for survival in acidic conditions.
Tanaka
Y
Y
Tokyo University of Marine Science and Technology, Minato, Tokyo, Japan.
Kimura
B
B
Takahashi
H
H
Watanabe
T
T
Obata
H
H
Kai
A
A
Morozumi
S
S
Fujii
T
T
D000222:Adaptation, Physiological; D026905:Amino Acid Transport Systems / Q000235:genetics; D017920:Antiporters / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002103:Cadaverine / Q000378:metabolism; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism*; D005516:Food Microbiology; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014736:Vibrio parahaemolyticus / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D014774:Virulence / Q000235:genetics
D026905:Amino Acid Transport Systems; D017920:Antiporters; D001426:Bacterial Proteins; C088101:CadB protein, Bacteria; D012333:RNA, Messenger; D002262:Carboxy-Lyases; C021520:lysine decarboxylase; D002103:Cadaverine