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

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Abstract
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’ (μ≅ 13 800 cal mol-1), the critical temperature (Tcrit≅ 17.9d̀C) and the notional minimum growth temperature (To≅ 3.6d̀C). Preincubation of Ent. faecalis cells at low temperatures (8–16d̀C) during periods corresponding to their generation time resulted in an increased ability of the bacterial cells to withstand short periods of freezing/thawing (-20d̀C/+37d̀C) challenge. Moreover, the increase of the incubation period at low positive temperature led to a higher degree of adaptation.