Transcription of the lambdadv plasmid and inhibition of lambda phages in lambdadv carrier cells of Escherichia coli

A CI-independent form of replicative inhibition: turn off of early replication of bacteriophage lambda

Several earlier studies have described an unusual exclusion phenotype exhibited by cells with plasmids carrying a portion of the replication region of phage lambda. Cells exhibiting this inhibition phenotype (IP) prevent the plating of homo-immune and hybrid hetero-immune lambdoid phages. We have attempted to define aspects of IP, and show that it is directed to repλ phages. IP was observed in cells with plasmids containing a λ DNA fragment including oop, encoding a short OOP micro RNA, and part of the lambda origin of replication, oriλ, defined by iteron sequences ITN1-4 and an adjacent high AT-rich sequence. Transcription of the intact oop sequence from its promoter, p(O) is required for IP, as are iterons ITN3-4, but not the high AT-rich portion of oriλ. The results suggest that IP silencing is directed to theta mode replication initiation from an infecting repλ genome, or an induced repλ prophage. Phage mutations suppressing IP, i.e., Sip, map within, or adjacent to cro or in O, or both. Our results for plasmid based IP suggest the hypothesis that there is a natural mechanism for silencing early theta-mode replication initiation, i.e. the buildup of λ genomes with oop(+)oriλ(+) sequence.

The DNA sequence of the phage lambda genome between PL and the gene bet

We have determined 3,400 base pairs of DNA sequence from the phage gamma genome which starts to the right of PL and runs to the left into the gene bet. The sequence thus includes the genes, N, ral, Ea10, cIII, kil and gam, as well as the transcription terminators TL1 and TL2. One surprising feature of the sequence is the presence in the region expected to be occupied by ral of a long open reading frame that, if it is expressed, would have to be transcribed from left to right, or counter to transcription from PL.

Purification and some properties of presumptive tof gene product of Coli phage 434

The presumptive tof gene product of Coli phage 434 has been purified from cells carrying lambdaimm434cIdv plasmid known to contain only some of the "early" genes of phage 434 and lambda. It was detected and tentatively identified as tof protein primarily by its ability to specifically bind to phage 434 DNA. The protein has a molecular weight of about 11,000 and requires Mg2+ for specific DNA binding, unlike 434 cI-repressor.

Properties of adenyl cyclase and cyclic adenosine 3',5'-monophosphate receptor protein-deficient mutants of Escherichia coli

Several spontaneous cya and crp mutants of Escherichia coli have been selected as clones simultaneously resistant to phage lambda and nalidixic acid and characterized. Both cya and crp mutants have been found to grow as cocci with increased doubling times. They have increased resistance to some mutagens (methylmethanesulfonate, ultraviolet light, gamma rays), antibiotics (nalidixic acid, ampicillin), phages (lambda, T6), sublethal heat and hypotonic shock, and decreased resistance to neutral detergents (sodium dodecyl sulfate, sodium deoxycholate), a protein synthesis inhibitor (streptomycin), and a respiratory inhibitor (sodium azide). The nature of changes in cell parameters indicate fundamental alterations in the envelope structure of the cya and crp mutant cells. The new cya and crp mutants have been found to be multiply carbohydrate negative and nonmotile in conformity with similar previously isolated mutants. Studies of revertants and phi80 cya+ and phi80 cya transductants indicated that the pleiotropic phenotype is related to a single mutational event at the cya or the crp locus in the mutants.