Role of catalase and oxyR in the viable but nonculturable state of Vibrio vulnificus

Vibrio vulnificus has proven difficult to culture from water or shellfish during winter months, which is attributed to the viable but nonculturable (VBNC) state. Because reactive oxygen species were found to be involved in the low temperature-induced entrance of V. vulnificus into this state, we generated an oxyR mutant which lacks catalase activity. This strain is nonculturable on solid media even at ambient temperature, due to the presence of H2O2 in such media. Low temperature incubation of the parent resulted in loss of catalase activity, making the cells H2O2 sensitive, and paralleling the loss of culturability (entry into the VBNC state). Thus, cells of V. vulnificus in the VBNC state are likely exhibiting this response to low in situ temperature and only When the artificial condition of laboratory culture is attempted are the cells nonculturable due to cold-induced loss of catalase activity. To our knowledge, this is the first study providing direct evidence for the metabolic basis of nonculturability and the viable but nonculturable state. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.