Characterization of conditional lethal mutants of bacteriophage P2.

Abstract

Conditional lethal mutants representing 18 different P2 genes have been characterized. Mutants affected in 15 of these 18 genes cause normal lysis of non-permissive cells, although phage production is blocked. In vitro reconstitution experiments show that these 15 genes can be classified into a group of 6 head genes and a group of 9 tail genes. Mutants affected in the three genes A, B, and K do not cause normal lysis when they infect non-permissive cells. The K function is probably involved in lysis, whereas A and B are “early” functions. A mutation in gene A is sufficient to block cell killing both after infection and after derepression of a prophage. All P2 functions that can kill the host cell are thus directly or indirectly controlled by the A function. The two “early” functions are apparently not required for lysogenization, since non-permissive cells are efficiently lysogenized by A and B mutants. Temperature-shift experiments suggest that the two “early” functions are required even during late stages of an infection. Although P2 and λ have very different properties there are strong similarities in the arrangement of genes on the genetic maps of the two phages.