Formation of nonculturable Vibrio vulnificus cells and its relationship to the starvation state

Abstract

Entry into the viable but nonculturable state by the human bacterial pathogen Vibrio vulnificus in artificial seawater microcosms was studied. In contrast to the long-term culturability exhibited by cells incubated under these starvation conditions at room temperature, cells exposed to a temperature downshift to 5 degrees C exhibited an immediate decrease in culturability. Cells incubated at low temperature exhibited a morphological change from rods to cocci but demonstrated no reductive division. Of 10 factors studied which might affect the nonculturable response in V. vulnificus, only the physiological age of the cells was found to significantly affect the rate at which cells became nonculturable. The nonculturable response appears to be related to the starvation response, as prestarvation at room temperature for 24 h was found to eliminate the nonculturable response of cells subsequently incubated at 5 degrees C. This observation suggests that the synthesis of starvation proteins may repress the viable but nonculturable program displayed during low-temperature incubation. The possible ecological significance of these findings is discussed.