Temperate Coliphage HK022: Clear Plaque Mutants and Preliminary Vegetative Map

Abstract

Wild type phage HK022 was mutagenized by N-methyl-N''-nitro-N-nitrosoguanidine to induce clear plaque mutants. A total of 225 clear plaque mutants were isolated, and 198 of these were assignable to 2 complementation groups of the corresponding cistrons which were designated as cI and cII, respectively. Approximately 25% of the c mutants were temperature-sensitive (cts); producing turbid plaques at 32.degree. C and clear plaques at >EQ 38 C. From complementation tests involving cI and cII mutants, bacteria [Escherichia coli] lysogenic for cII prophage were frequently obtained. Double lysogens harboring a cI and a cII prophage were infrequently found, and single lysogens harboring only a cI prophage were not recovered. Bacterial lysogens harboring a prophage carrying a cts mutation in the cI cistron were readily obtainable. Such lysogens show a lethal phenotype at >EQ 40.degree. C although they appear to be fully viable at 32.degree. C. By incubation of lysogens harboring a cts mutant of the cI cistron at 42.degree. C, cryptic lysogens which are non-immune but harbor at least 1 of the phage sus+ alleles can be isolated. Genetic data involving cI, cII and 2 complementing sus mutants of essential genes are presented. From these data the vegetative map is deduced: sus4-cII-cI-sus3.