Resistance to environmental stresses by Vibrio vulnificus in the viable but nonculturable state

Vibrio vulnificus is responsible for 95% of all seafood-associated fatalities in the United States. When water temperatures drop below c.13 degrees C, the cells enter into the viable but nonculturable (VBNC) state wherein they are unable to grow on routine media but retain viability and the ability to return to the culturable state. The aim of this study was to determine whether V.vulnificus cells in the VBNC state are protected against a variety of potentially lethal challenges (heat, oxidative, osmotic, pH, ethanol, antibiotic and heavy metal) and to examine genetic regulators that might underlie such protection. The data presented here indicate that VBNC cells of this pathogen are protected against a wide variety of stresses and retain the ability to return to the culturable state. Surprisingly, we found no significant difference in the expression of relA and spoT between VBNC and logarithmic cells, nor any significant difference in the expression of rpoS in the case of the clinical (C) genotype of this pathogen. However, expression of relA was significantly different in VBNC cells of the environmental (E) genotype compared with logarithmic cells. This might account for findings indicating an enhanced ability for E-genotype cells to withstand environmental changes better than C-genotype cells.