Physiological response of Enterococcus faecalis JH2-2 to cold shock: Growth at low temperatures and freezing/thawing challenge

Growth at low positive temperatures and induced phenotypic resistance to extreme cold temperature (freezing/thawing cycles) of Enterococcus faecalis were investigated. The effect of low temperatures on the specific growth rates was studied; use of Arrhenius profile and Ratkovsky 'square-root' model allowed determination of the 'temperature characteristic' (mu congruent to 13800 cal mol(-1)), the critical temperature (T(crit)congruent to 17.9 degrees C) and the notional minimum growth temperature (T-0 congruent to 3.6 degrees C). Preincubation of Ent. faecalis cells at low temperatures (8-16 degrees C) during periods corresponding to their generation time resulted in an increased ability of the bacterial cells to withstand short periods of freezing/thawing (-20 degrees C/+37 degrees C) challenge. Moreover, the increase of the incubation period at low positive temperature led to a higher degree of adaptation.