Transduction of Streptococcus pyogenes K 56 by temperature-sensitive mutants of the transducing phage A 25.

Experiments aimed at increasing the efficiency of transduction by the virulent group A strepto­ coccal phage A 25 were carried out using temperature-sensitive phage mutants. Lysates of phages carrying ts mutations proved to transduce more efficiently than wild type lysates, the order of in­ creasing effectiveness being ts+ < tsl ~ ts2 < tsl —2. Differential survival of the recipient, K 56, appeared to be the principal reason for the improvement of transduction when cells decapsulated by hyaluronidase were transduced at the restrictive temperature. In transduction of encapsulated recipient cells, in which the superiority of ts lysates was less pronounced, the possibility was con­ sidered that mutant lysates might contain higher fractions of transducing particles than wild type lysates produced under parallel conditions. The transducing activity of wild type lysates depended strongly on the temperature at which the phage had multiplied on the donor strain, the frequency of transduction increasing with decreasing temperature. Since the minimal latent period of the phage varied roughly in the same way with temperature, a connection is suggested between the time required for phage multiplication and the proportion of transducing particles formed.