Restart of exponential growth of cold-shocked Yersinia enterocolitica occurs after down-regulation of cspA1/A2 mRNA

The cellular content of major cold shock protein (MCSP) mRNA transcribed fr om the tandem gene duplication cspA1/A2 and growth of Yersinia enterocoliti ca were compared when exponentially growing cultures of this bacterium were cold shocked from 30 to 20, 15, 10, 5, or 0 degrees C, respectively. A cle ar correlation between the time point when exponential growth resumes after cold shock and the degradation of cspA1/A2 mRNA was found. A polynucleotid e phosphorylase-deficient mutant was unable to degrade cspA1/A2 mRNA proper ly and showed a delay, as well as a lower rate, of growth after cold shock. For this mutant, a correlation between decreasing cspA1/A2 mRNA and restar t of growth after cold shock was also observed. For both wild-type and muta nt cells, no correlation of restart of growth with the cellular content of MCSPs was found. We suggest that, after synthesis of cold shock proteins an d cold adaptation of the cells, MCSP mRNAs must be degraded; otherwise, the y trap ribosomes, prevent translation of bulk mRNA, and thus inhibit growth of this bacterium at low temperatures.