Novel segregation patterns of infecting-mutant genotypes in plate complementation tests among amber mutants of bacteriophage BF23

Abstract

Amber mutants of bacteriophage BF23 were classified into two functional groups, types I and II, by the yields of the infecting-mutant genotypes in plate complementation tests. Type I mutants produced their genotypes at levels more than 20% of the total progeny phages, and type II mutants did so at levels of less than 5%. Comparison of the results of plate complementation tests with those of extract complementation tests revealed that all the type I mutants were defective in the tail formation, while most type II mutants were defective in the formation of either mature heads (type Ila) or both mature heads and tails (type Ilb). Since in extract complementation tests the activated phages are always of genotypes corresponding to mutations defective in only the tail formation, the plate complementation test is comparable with the extract complementation test when judged on the basis of the yield of the mutant genotypes. Of 29 complementation groups, 8 type I, 14 type Ila, and 5 type lIb mutants were identified. Previously, amber mutations of BF23 were mapped on four genetic segments. These segments were ordered in one linkage map by crosses between deletion and amber mutants.

Relationships among genes and gene products of bacteriophage BF23

“…2d and f). These results indicate that E12 is encoded by the deletable region located between genes 5 and 6 (see the genetic map of BF23 [9]) and is dispensable for the propagation of BF23.…”

“…We have shown that amber mutants of BF23 are classified into two functional groups, types I and II, by means of plate complementation tests (9). Type I mutants were shown to be defective in the formation of tails by the extract complementation tests, while most type II mutants were defective in the formation of either mature heads (type IIa) or both mature heads and tails (type IIb).…”

Regulation of the temporal synthesis of proteins in bacteriophage BF23-infected cells

“…The mutant phages used were am57 (gene 1), amH30 (gene 2), amHIll (gene 10), amH85 (gene 14), and am182 (gene 19) (17,19). Pulse-labeling of phage-encoded proteins.…”

“…RESULTS Pulse-labeling pattern of protein synthesis. Five amber mutants, amS7 (gene 1), amH30 (gene 2), amHIll (gene 10), amH85 (gene 14), and am182 (gene 19), were classified as type Ilb mutants and shown to alter considerably their patterns of protein synthesis in the infected cells (17,19). To further characterize these mutants, pulse-labeling patterns of protein synthesis in cells infected with each mutant were compared with that in the wild-type-infected cells presented in Fig.…”

“…In an accompanying report, we show the considerable alteration of the patterns of protein synthesis in the cells infected with amber mutants defective in genes 1, 2, 10, 14, and 19 (19). These mutants were classified as type IIb by genetic complementation tests (17). To understand the temporal control of gene expression of BF23, we further char-acterized these mutants.…”