FREEZING OF BACTERIOPHAGE-T4 - TEMPERATURE AND RATE EFFECTS AS A FUNCTION OF SALT CONCENTRATION

When frozen in dilute NaCl solutions, phages T4B and T4D are much more sensitive to rapid thawing than their corresponding osmotic shock-resistant mutants, T4Bos and T4Dos. We hypothesize that the inactivation of shock-sensitive phage when rapidly warmed is due to the osmotic shock that occurs as salts concentrated during freezing are rapidly diluted during rapid thawing. This hypothesis is strengthened by a genetic analysis demonstrating that a mutant isolated by freezing and rapid thawing is identical to a shock-resistant mutant isolated by osmotic shock. However, in contrast to the situation in dilute solution (< 0.1 molal), phages T4B and T4Bos were equally sensitive when frozen in concentrated NaCl solutions, regardless of cooling or warming rates. Phage inactivation under these conditions was a step function of subzero temperature, just as is the complete crystallization of water and the precipitation of all salts in a solution undergoing freezing. Therefore, the complete solidification of the phage suspension apparently is a major factor in the inactivation of T4 phage frozen in solutions 0.1 molal or greater in concentration. © 1969.