Change of protein profiles in the induction of the viable but nonculturable state of Vibrio parahaemolyticus.

This work reports on the metabolic response in the induction of the viable but nonculturable (VBNC) state of the seafood enteropathogen Vibrio parahaemolyticus, as determined by analyzing the corresponding change in protein profiles. V. parahaemolyticus ST550 was incubated at 4 degrees C in the Morita mineral salt-0.5% NaCl medium to induce the VBNC state in six weeks. Starving the cells by incubation at 25 degrees C for 24 h prior to 4 degrees C incubation inhibited the cells from entering VBNC state. Protein profiles were determined by two-dimensional polyacrylamide gel electrophoresis and the proteins which were enhanced in the VBNC induction/VBNC state or strongly down-regulated in the starved cells were identified by mass spectrophotometry. The 13 up-regulated proteins are known to be associated with transcription (two homologues of alpha subunit DNA-directed RNA polymerase, phosphoribosylaminoimidazole carboxamide formyltransferase/IMP cyclohydrolase), translation (ribosomal protein S1, two homologues of elongation factor TU, elongation factor EF-G), ATP synthase (F1 alpha subunit), gluconeogenesis-related metabolism (dihydrolipoamide acetyltransferase, glyceraldehyde 3-phosphate dehydrogenase), antioxidants (2 homologues of peroxiredoxins, AhpC/Tsa family) and a conserved hypothetical protein with unknown function. Expressions of the genes encoding four of these proteins were at high levels in the second week of VBNC induction; declined afterwards, and were down-regulated in the starved cells. These proteins may play important roles in the induction or maintenance of VBNC V. parahaemolyticus. The results of this investigation improve our understanding of the metabolic activities in the VBNC state of bacteria.