In vivo repair of bacteriophage t5 DNA: an assay for viral growth control

Colicin Ib does not cause plasmid-promoted abortive phage infection of Escherichia coli K-12

A 2.2 kilobase (kb) fragment of ColIdrd-1 cloned in pBR325 causes phage T5 and BF23 infections of Escherichia coli K-12 to abort. This abortive infection is associated with leakage of beta-galactosidase from the cell. A recombinant plasmid containing a 2.8 kb fragment of ColIdrd-1 encodes colicin Ib but fails to cause abortive infection. Tn5 and Tn10 insertions into ColIdrd-1 that abolish colicin Ib production have no effect on the abortive infection phenotype. These findings are inconsistent with a previously proposed role for colicin Ib in causing phage infections to abort.

Role of the T5 gene D15 nuclease in the generation of nicked bacteriophage T5 DNA

The processing of newly replicated concatameric T5 DNA into both single stranded DNA changed of unit length and single-stranded fragments of sizes comparable to those found in mature T5 virion DNA occurs in the absence of late T5 protein synthesis. The formation of unit-length, single-stranded DNA chains does not require the early T5 gene D15 nuclease: however, the subsequent formation of the single-stranded fragments does require that the D15 nuclease be functional. A reexamination of the properties of the purified D15 nuclease under a variety of conditions showed that, in addition to functioning as a 5' leads to 3' exonuclease, the enzyme can also introduce endonucleolytic scissions into mature T5 DNA in a reaction that requires duplex T5 DNA and preexisting, single-stranded interruptions.

Incompatibility and bacteriophage inhibition properties of N-1, a plasmid belonging to the H2 incompatibility group

N-1, a plasmid isolated from a strain of Shigella flexneri in Japan more than 10 years ago, mediates the phage inhibition phenotype which has recently been found to be characteristic of plasmids of the H2 incompatibility group. Using the criteria of phage inhibition, surface exclusion and incompatibility, the N-1 plasmid is shown to be closely related to H2 plasmids isolated from non-typhoid salmonella and distantly related to H1 plasmids isolated from Salmonella typhi. Plasmids of other incompatibility groups did not show the H2 type of phage inhibition.

Isolation and genetic characterizaion of Escherichia coli K-12 mutations affecting bacteriophage T5 restriction by the ColIb plasmid

A mutant derivative of Escherichia coli K-12 has been isolated which is permissive for bacteriophage T5 infection even when harboring a wild-type ColIb plasmid. The fully permissive phenotype was the result of two mutations that are located near the rpsL-rpsE region on the E. coli chromosome and are recessive to the wild-type alleles. These mutations had little or no effect on induction of colicin synthesis and did not affect the expression of antibiotic resistance by the resistance plasmids R64drd11 or R1drd19. Cells harboring the mutant alleles grew more slowly than isogenic wild-type derivatives in either minimal or complete media.