Escherichia coli K-12 and B contain functional bacteriophage P2 ogr genes

Abstract

The bacteriophage P2 ogr gene encodes an essential 72-amino-acid protein which acts as a positive regulator of P2 late transcription. A P2 ogr deletion phage, which depends on the supply of Ogr protein in trans for lytic growth on Escherichia coli C, has previously been constructed. E. coli B and K-12 were found to support the growth of the ogr-defective P2 phage because of the presence of functional ogr genes located in cryptic P2-like prophages in these strains. The cryptic ogr genes were cloned and sequenced. The Escherichia coli rpoA109 mutation, which causes an amino acid substitution in the a subunit of the RNA polymerase, blocks transcription of the P2 late genes (21,56). This block is overcome by suppressor mutations in the P2 ogr gene (56); thus, it appears that Ogr interacts with the RNA polymerase ao subunit in initiation of transcription from the P2 late promoters. Interactions between the ac subunit and other positive regulatory proteins have been implied by the isolation of several rpoA mutations which affect the transcription of different positively regulated E. coli genes (22,25,44,47) and also by recent studies of the E. coli cyclic-AMP receptor protein (34, 35).As a part of our investigations concerning the Ogr protein function and the regulation of its gene, we have previously reported the construction of an ogr-defective mutant phage, P2 dellS, which carries a deletion in the C-terminal half of the ogr gene (9). P2 dellS grows lytically on E. coli C, the standard host for phage P2, only if the Ogr protein is provided in trans from an ogr-expressing plasmid, demonstrating that the ogr gene is essential for P2 lytic growth. In this paper, we report that E. coli B and K-12 strains are able to support growth of P2 dell5 and that this ability is due to the presence of chromosomally located ogr genes carried by cryptic prophages. The presence of an ogr gene in E. coli * Corresponding author. K-12 has recently also been demonstrated by Barreiro andHaggard-Ljungquist (4). When the P2 ogr gene is compared with the cryptic genes, there are few differences in the nucleotide sequences, and most of the differences are silent base substitutions. MATERIALS AND METHODSBacteria, phages, and plasmids. Bacterial strains, phages, and plasmids are listed in Table 1. Strain C-2156 was used as a standard host for P2 dellS (11). The culture media were L broth and L agar (52). Plasmid-containing strains were grown in media containing 100 ,ug of ampicillin per ml (pBluescript SK+ and its derivatives) or 12.5 p,g of tetracycline per ml (pNB56).Burst size determination. Bacteria were grown in L broth at 37°C to an optical density at 600 nm of 0.2, collected by centrifugation at 9,000 x g for 2 min, and resuspended in one-third the original volume of ice-cold L broth containing 5 mM CaCl2. The cells were infected with P2 dellS at a multiplicity of infection of 0.1 and then incubated at 37'C for 8 min for adsorption of the phage. The infected cells were collected by centrifugation at 9,000 x g for 2 min at 4°C and washed ...

Mutations affecting two adjacent amino acid residues in the alpha subunit of RNA polymerase block transcriptional activation by the bacteriophage P2 Ogr protein

“…Each of the chromosomal rpoA mutations reported to affect positive control in E. coli K-12 was moved by transduction into prototrophic C strain E. coli C-la, and activation of cat expression from pFCAT100 by Ogr (pGC57) or 8 (pGVB1) was assayed ( (2,59). This raises the possibility that such genes, if present in the strains in which the rpoA mutations were tested, could mask an effect of the polymerase mutation on normal P2 late-gene expression.…”

Genetic evidence for an activator required for induction of colicin-like bacteriocin 28b production in Serratia marcescens by DNA-damaging agents

“…It has been shown that E. coli K-12 and B have a chromosomal ogr gene, probably originated by an aberrant P2 prophage excision event (4,47). No SOS-like sequences have been found in this chromosomal ogr promoter, explaining the lack of mitomycin inducibility of the bss gene transcription in E. coli, even if this ogr gene product could interact with the bss gene promoter.…”

“…(C) Amino acid alignment among deduced regC gene product, S. marcescens SM6 deduced nucC gene product (GenBank nucleotide sequence accession no. U11698), phage B protein 186 (26), phage P2 protein Ogr in E. coli (E. c.) (4,47), phage P2 protein Ogr (5), phage ⌽-R73 protein ␦ (49), and phage P4 protein ␦ (22). Asterisks denote conservated Cys residues, probably defining a zinc finger domain.…”

Attachment sites for bacteriophage P2 on the Escherichia coli chromosome: DNA sequences, localization on the physical map, and detection of a P2-like remnant in E. coli K-12 derivatives

“…Since the ogr gene has a promoter located in the spacer region between genes D and ogr (14,28), the ogr gene is probably expressed. In fact, an ogr activity has been observed in E. coli B and K-12 strains (34).…”