Expression of the unassembled capsid protein during infection of Shigella sonnei by bacteriophage T7 results in DNA damage that is repairable by bacteriophage T3, but not T7, DNA ligase

The genome sequence of Yersinia pestis bacteriophage phiA1122 reveals an intimate history with the coliphage T3 and T7 genomes

The genome sequence of bacteriophage phiA1122 has been determined. phiA1122 grows on almost all isolates of Yersinia pestis and is used by the Centers for Disease Control and Prevention as a diagnostic agent for the causative agent of plague. phiA1122 is very closely related to coliphage T7; the two genomes are colinear, and the genome-wide level of nucleotide identity is about 89%. However, a quarter of the phiA1122 genome, one that includes about half of the morphogenetic and maturation functions, is significantly more closely related to coliphage T3 than to T7. It is proposed that the yersiniophage phiA1122 recombined with a close relative of the Y. enterocolitica phage phiYeO3-12 to yield progeny phages, one of which became the classic T3 coliphage of Demerec and Fano (M. Demerec and U. Fano, Genetics 30:119-136, 1945).

Complete nucleotide sequence and likely recombinatorial origin of bacteriophage T3

We report the complete genome sequence (38,208 bp) of bacteriophage T3 and provide a bioinformatic comparative analysis with other completely sequenced members of the T7 group of phages. This comparison suggests that T3 has evolved from a recombinant between a T7-like coliphage and a yersiniophage. To assess this, recombination between T7 and the Yersinia enterocolitica serotype O:3 phage phiYeO3-12 was accomplished in vivo; coliphage progeny from this cross were selected that had many biological properties of T3. This represents the first experimentally observed recombination between lytic phages whose normal hosts are different bacterial genera.

Expression of gene 1.2 and gene 10 of bacteriophage T7 is lethal to F plasmid-containing Escherichia coli

Plasmids expressing bacteriophage T7 gene 1.2 or gene 10 DNA transform F plasmid-containing strains of Escherichia coli only at low efficiency, though they transform plasmid-free strains normally. The gene products T7 gp1.2 and T7 gp10 appear to be the toxic agents, and their effects are directed towards the product of the F pifA gene, PifA. T7 gp1.2 and gp10 are also the two targets of the pif exclusion system of F, and their synthesis normally triggers the abortive infection of T7 in pifA+ hosts. The properties of plasmids containing T7 gene 1.2 or 10 suggest that they can be used to study the molecular mechanisms of phage exclusion in model systems that avoid the pleiotropic dysfunctions associated with an abortive infection.

The bacteriophage T4 gene mrh whose product inhibits late T4 gene expression in an Escherichia coli rpoH (sigma 32) mutant

In an Escherichia coli rpoH mutant (affecting sigma 32, heat-shock sigma factor) infected at high temperatures with wild-type T4 phage, late T4 transcription and consequently progeny production are dramatically impaired. This defect is due, in part, to insufficient activity of sigma 70 [Frazier and Mosig, J. Bacteriol. 170 (1988) 1384-1388], which is necessary to initiate early T4 transcription. Unexpectedly, however, we found that, in this rpoH host, late T4 transcription is also impaired when the temperature is raised from 30 to 42 degrees C late after infection, when T4 transcription is directed by the T4-encoded sigma factor, sigma gp55. Here, we show that a T4 gene that we call mrh (modulates rpoH), located at 14 kb on the T4 map, is responsible for the inhibition of late T4 transcription in the rpoH mutant host. T4 deletion mutants that lack the mrh gene can produce progeny in the rpoH host, but the Mrh protein, provided in trans from a plasmid-borne mrh gene, inhibits this growth. We have cloned and sequenced this T4 gene and synthesized the Mrh protein in a T7 RNA polymerase-dependent expression system. The Mr of the Mrh protein deduced from the nucleotide sequence is 13419. Gene mrh is cotranscribed with several other, yet unidentified genes, both from an early promoter downstream from the late soc gene (encoding the small outer capsid protein) and from the late soc promoter further upstream.(ABSTRACT TRUNCATED AT 250 WORDS)

Mutants of bacteriophage T7 that escape F restriction

Mutants of bacteriophage T7 that escape F restriction have been isolated. Two mutations in gene 10, which codes for the capsid protein, and one mutation in gene 1.2 are required for these phages to grow on F-containing strains. The products of these two genes are the two targets of the exclusion system; the presence of either wild-type product results in an abortive infection. Phages that grow normally in male hosts still lead to membrane dysfunction and nucleotide efflux from the infected cell. This type of membrane damage and the abortive infection are therefore separable phenomena.

A single-base change in gene 10 of bacteriophage T7 permits growth on Shigella sonnei

Bacteriophage T7 can extend its host range to include Shigella sonnei D2 371-48 by a mutation called ss found in the T7 major capsid protein, the gene 10 product. We show that a single A-to-C transversion at position 23150 in the T7 genome is responsible for the T7 ss mutant phenotype that allows the phage to avoid DNA degradation and undergo productive infection. The ss mutation causes an amino acid substitution of proline for glutamine at position 61 of the 344-amino-acid T7 major capsid protein.

Sequence of a conditionally essential region of bacteriophage T3, including the primary origin of DNA replication

The 3526 base-pair nucleotide sequence from near the end of bacteriophage T3 gene 1 to within the coding sequence of gene 2.5 is given. It includes the complete coding sequences for nine known or presumptive proteins, most of which are only conditionally essential for phage growth. The sequence includes five promoters for the phage RNA polymerase, the terminator for early (host enzyme-catalyzed) transcription, and two recognition sites for RNAase III. The primary origin of T3 DNA replication that is utilized by the phage in vivo has been localized to a 142 base-pair region. It has several features in common with the phage T7 origin of DNA replication, and exhibits considerable homology to recognition sites for the mRNA processing enzyme RNAase III. It is proposed that the primary origin of T3 DNA replication may have evolved directly from an RNAase III recognition site. The deletions present in a number of T3 mutant strains and the location of the nucleotide changes in several T3 strains that are defective in their ability to grow on F+-containing strains or on optA mutant hosts have been determined. We discuss how T3 may have become genetically isolated from its relatives in the T7-T3 group and simultaneously acquired novel biological and biochemical properties.

In vitro packaging of heteroduplex bacteriophage T7 DNA: evidence for repair of mismatched bases

Heteroduplex DNA molecules that were wild type or contained combinations of amber, missense, and temperature-sensitive mutations were prepared from bacteriophage T7. These DNA molecules were then encapsulated in in vitro packaging reactions so as to produce infective T7 phage. The genotypes of the phage were examined to determine the degree to which mismatched base pairs in the heteroduplex had been corrected. The data show that conversion of the mismatches took place either during in vitro packaging or immediately after infection of either an Escherichia coli or Shigella sonnei host. The mode of mismatch conversion observed in these experiments was independent of the host mutH, mutL, mutS, and uvrD genes. There was no significant amount of discrimination between markers on either of the two complementary strands. The observed frequency of conversion of a mismatch depended on the genetic marker being monitored and on experimental conditions but was generally in the range between 5 and 30%.