Identification and characterization of mutations in Escherichia coli that selectively influence the growth of hybrid lambda bacteriophages carrying the immunity region of bacteriophage P22

Abstract

Mutations in two Escherichia coli genes, sipA and sipB, result in a specific inhibition of the growth of certain hybrid lambdoid bacteriophages, A immRI2, that have the early regulatory regions and adjacent genes from bacteriophage P22. The sipB391 mutation maps near minute 56 and exerts the strongest inhibitory effect on the growth of the hybrid phages. The sipAl mutation maps near ninute 72 and plays an auxiliary role: enhancing the action of sipB391. Such a role is not limited to sipAl, since there is a similar enhancement by the nusAl and nusE71 mutations. The Sip-imposed restriction on the growth of X immP22 phages is not observed if the phage carries a mutation in the cl gene. Perhaps this reflects the fact that the cl product regulates phage DNA replication and is a major determinant in the decision governing whether the phage takes the lytic or lysogenic pathway. Consistent with this idea is the observation that A immP2 DNA replication is severely inhibited in bacteria carrying the sipB391 mutation. It is suggested that sip mutations exaggerate the normal role of cl in limiting lytic growth. This causes a failure in the expression of sufficient amounts of some or all of the lytic gene products required for phage growth.Host mutants that influence the growth of lambdoid bacteriophages have served as remarkable tools both for studying the action of phage gene products and for identifying genes whose products play important roles in the physiology of the host (19). One class of host factors is those that influence phage products active in the process of establishing repressor synthesis. The hfl (high frequency of lysogeny) (4, 5; F. Banuet and I. Herskowitz, personal communication) and the him and hip (host integration mediation and host integration protein) (33,41,44) genes control the level of cII protein, a bacteriophage X protein that plays a pivotal role in the decision determining whether the infecting phage follows the lytic or lysogenic route. This regulation is exerted in three ways: (i) controlling the establishment of cI (repressor) expression (26, 56); (ii) stimulating expression of the gene int, whose product is required for prophage integration (16); and (iii) reducing expression of late genes (13,40).The cl gene of lambdoid bacteriophage P22 maps in the same relative position as the cIT gene of X and encodes a protein that serves functions analogous to those of the cII protein (35, 52). P22, whose natural host is Salmonella typhimurium, is unable to infect Escherichia coli because it is unable to adsorb. Hybrid phages that are able to grow in E. coli have been engineered under special conditions by using in vivo recombination (10, 23, 28, 58). Some of these hybrids carry the early regulatory and replication genes of P22 and the late morphogenic genes of X including those encoding tail proteins. The relevant genetic structures of X and P22 are shown in Fig. 1. The hybrids used in our experiments carry the early regulatory region from P22 (immC), which includes the c2 (repressor) gene, and t...

Lon Protease Degrades Transfer-Messenger RNA-Tagged Proteins

“…The clpX::Kan strain was prepared through P1 transduction of W3110 with a P1 lysate of BW25113 ⌬clpX from the Keio collection (4). -P22 hybrid bacteriophages immP22 c2-5 dis and immP22 c1-7 dis have been described previously (46). Plasmid pPW500 (31) encodes -cI-N-trpAt nonstop reporter mRNA regulated by a P TRC promoter.…”

“…SmpB and tmRNA functions are required for lytic development of the immP22 c2-5 dis hybrid phage but not for lytic development of the related immP22 c1-7 dis phage (29,38,46,52). The molecular basis for this strict dependence of immP22 c2-5 dis hybrid phage on SmpB and tmRNA is currently not clear.…”

Excision of a P4-like cryptic prophage leads to Alp protease expression in Escherichia coli

“…7). Friedman and coworkers found that the sipB phenotype of certain E. coli mutant hosts corresponds to the excision of the CP4-57 cryptic prophage (39,48). The mutant phenotype is failure of a X-P22 dis hybrid phage to grow.…”

Role for 10Sa RNA in the growth of lambda-P22 hybrid phage

“…We have previously reported the isolation of a variant of E. coli K-12 that, unlike its parent, fails to support growth of certain hybrid phages formed by recombination between E. coli phage X and Salmonella typhimurium phage P22 (38). This E. coli variant, however, supports growth of and most other lambdoid phages.…”

“…The nonessential immI region, which has no analog in X, encodes the ant (antirepressor) gene and associated regulatory genes (42). The growth of X-P22 hybrids in E. coli with the sipB391 mutation depends on the extent of P22 genetic material substituted for genetic material and on the nature of the sipA allele carried by the bacterium (38). E. coli with the sipB391 mutation and what we have arbitrarily designated the wild-type sipA allele fails to support growth of a X-P22 hybrid carrying the immI-through-immC region of P22 (Fig.…”