Growth phase is among the most important factors which may
influence the extent of induced stress response in microorganisms
(Jørgensen et al., 1999; McMahon et al., 2000; De Angelis et al.,
2004; Yeung and Boor, 2004). Jørgensen et al. (1999) reported that
the magnitude of heat shock induced thermotolerance in Listeria
monocytogenes was lower in stationary cultures compared with
exponentially growing cultures. McMahon et al. (2000) indicated
that the thermal resistance of Yersinia enterocolitica and L. monocytogenes
was dependent on cell growth phase. They also reported
that the magnitude of change in heat resistance between heatshocked
and non-heat-shocked cells for exponential cultures was
greater than that for stationary cultures. Moreover, De Angelis et al.
(2004) observed that the extent of increased heat resistance of
Lactobacillus plantarum was greater with mid-exponential phase
cells than stationary phase cells after heat adaptation at 42 C for
1 h. Finally, Yeung and Boor (2004) reported that survival rates at
pH 3.6 for exponential phase cells of V. parahaemolyticus that had
been previously exposed to a sub-lethal acidic condition (pH 5.5)
were enhanced when compared with that of nonacid-adapted cells.
In contrast, acid adaptation impaired the survival of stationary
phase cells at pH 3.6.