The Vibrio vulnifcius cadBA genes encode a lysine/cadaverine antiporter and a lysine decarboxylase,whose combined activity leads to the synthesis and excretion of cadaverine to counteract external acidification.Lysine decarboxylase activity of V.vulnificus was induced at a low pH (pH 5.8),and the induction of lysine decarboxylase was regulated at the level of transcription.A primer extension analysis revealed that cadBA genes are organized as a single transcriptional unit,and that the transcription of cadBA begins at a specific site,consisting of a putative promoter Pcad.