Temperature-upshift-mediated revival from the sodium-pyruvate-recoverable viable but nonculturable state induced by low temperature in Ralstonia solanacearum: Linear regression analysis
2009
Imazaki, I.(National Agricultural Research Center, Tsukuba, Ibaraki (Japan)) | Nakaho, K.
The viable but nonculturable (VBNC) state is induced in stress-injured bacterial cells. VBNC cells lose their ability to grow on standard media, but some of the cells can recover on media supplemented with H2O2-degrading compounds such as sodium pyruvate (SP). Here, VBNC cells that can recover on such media are called SP-recoverable VBNC cells; VBNC cells that do not recover are called SP-unrecoverable VBNC cells. On the basis of previous findings, we hypothesized that cells of Ralstonia solanacearum in which low temperature had induced the SP-recoverable VBNC state would regain their ability to grow on standard solid media after exposure to moderate temperature. To test this, cell suspensions of R. solanacearum were incubated at 5degC. When SP-recoverable VBNC cells were the only culturable cells present, the cell suspensions were exposed to 25degC. The temperature upshift caused an initial rapid increase in the number of active cells able to grow on standard solid media, followed by a more gradual increase. Linear regression analyses suggested that this increase was not attributable to the regrowth of a low level of residual active cells. In addition, all the revived cells tested caused wilt symptoms in susceptible tomato plants. When SP-unrecoverable VBNC cells were the only viable cells present in the 5degC microcosms, the cell suspensions were exposed to 25degC. In this case, no culturable cells were detected. Therefore, these data strongly suggest that the SP-recoverable VBNC cells regained their ability to grow on standard solid media after the temperature upshift and that the revived cells were virulent.
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