PROPERTIES OF PHAGE PM2 H-MUTANTS AND THE HOST BACTERIUM ALTEROMONAS-ESPEJIANA

Mutants resistant to the wild-type phage PM2 (type C bacteria) were is olated from a culture of the marine bacterium Alteromonas espejiana BA L-31 (type B bacteria). The wide-host-range mutant phages PM2 r and PM 2 r2 capable of reproduction in type C bacteria were obtained. Unlike the wild-type phage (phage w), phage r did not reproduce in type B bac teria at temperatures above 26 degrees C, although both phages display ed similar kinetics of thermoinactivation at 45 degrees C. Phage r2, l ike phage w, reproduced at temperatures of up to 30 degrees C, i.e., i t was not a temperature-sensitive mutant (ts-mutant), The frequency of the w --> r mutation equaled 10(-6)-10(-7). The frequency of the reve rse mutation r --> w, resulting in the loss of both ts and wide-host-r ange properties, was the same, In type B bacteria, the frequency of mu tations toward resistance to phages w or r was 10(-6)-10(-8) per cell per generation. In type C bacteria, the frequency of mutations toward resistance to phage r was below 10(-6) per cell per generation; howeve r, over 10% of the bacteria formed colonies on Petri dishes with an ex cess of the phage, i.e., the mutation frequency in this system could n ot be determined by the standard procedure. In phage r lysates, an inh ibitor considerably decreasing the rate of the death of type C bacteri a induced by concentrated phage preparations (probably a reversible in hibitor of adsorption) was found.