Streptococcus thermophilus: physiological responses to cold shock

The adaptive response of a strain of Streptococcus thermophilus (ST105) iso lated from a commercial freeze-dried mixed yogurt starter was studied follo wing cold shock. ST105 cells propagated in M17 medium at 42 degreesC were h arvested during the early exponential growth phase and then grown at 15 deg reesC. Responses at 42 and 15 degreesC were compared at the physiological l evel and in terms of protein changes. An apparent generation time was estab lished almost 30 h following the cold shock. After cold shock, the expressi on of about 18 housekeeping proteins changed and 4 non constitutive protein s were induced.