Survival of Escherichia coli from freeze–thaw damage: influence of nutritional status and growth rate

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Abstract
The influence of nutritional status and growth rate on the cryosurvival of Escherichia coli was investigated. Organisms grown at rates between 0.1 and 0.6 h−1, under carbon- or nitrogen-limiting conditions all showed a basically similar cooling rate – survival profile; a peak of survival was noted in the lower cooling rate range (less than 100 C/min), a trough of minimum survival at 100 C/min, and increased survival as the cooling rate was increased to ultrarapid rates. Carbon-limited organisms showed a shift of the peak from 6 C/min for slowly grown organisms (D = 0.11) to 40 C/min at higher growth rates (D = 0.60 h−1); their survival at these peaks also showed a slightly upward trend. Nitrogen-limited organisms showed a similar trend of a shifting of the peak of survival. However, as the growth rate was increased, survival at this peak, and at other regions, decreased. For carbon-limited organisms, above 100 C/min, survival was growth rate independent, unlike nitrogen-limited organisms, which exhibited lower survivals as the cooling rate was increased in the ultrarapid range. The survival of both carbon-and nitrogen-limited organisms at the peak of survival showed a correlation with their carbohydrate and protein contents. The relevance of these findings is discussed.

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