A NEW CLASS OF TEMPERATURE CONDITIONAL LETHAL MUTANTS OF BACTERIOPHAGE T4D

100 mutants, able to grow on a K strain of E. coli at 42° but not at 25°, were isolated. These mutants were not uniform with respect to their responses to temperature on several other different strains of E. coli. When tested at 25° and 42° on E. coli KC112, CR63, B/5, and S/6/5, 12 different response patterns were evident. Complementation tests revealed 9 functional groups among 75 mutants tested. Further tests against amber mutants in known genes showed that mutants in 5 of these groups were defective in genes 17, 18, 20, 23, or 37 respectively. Genetic mapping by recombination confirmed these locations. Crosses also placed two mutants representing two groups, tentatively in gene 19, although certain anomalous behavior involving these mutats makes exact location uncertain. One group, consisting of 13 mutants, mapped close to gene 1 and appears to represent a previously undiscovered gene. The final group, containing 52 mutants, mapped 7.5 map units from an amber mutants in gene 42 although they complement with mutants in the gene. The non-random distribution of these mutants indicates that mutation to low temperature sensitivity on E. coli K is characteristic of particular genes, some of which are clustered on the genetic map. © 1968.