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PubMed1978

Regional replication of the bacterial chromosome induced by derepression of prophage lambda. III. Role of the replication in escape synthesis of gal operon.

Recent evidence suggests that the escape synthesis of gal operon following derepression of the prophage lambda in Escherichia coli K12 involves transcription originating at the lambda promoter (PL) to extend through gal under the conditions in which lambda DNA replication is prevented. Whether the observed expression of gal is due to transcription initiating at PL or at the bacterial promoter for gal (Pgal) was examined in the case of lambda DNA replication being normal. The experiments are based on that two types of transcription are distinguished from each other by the following properties: 1. Pgal-promoted transcription is inhibited by chloramphenicol, while PL-promoted transcription is not. 2. PL-promoted transcription suppresses the polar effect caused by nonsense mutation in a bacterial gene, while Pgal-promoted transcription does not do so. -he results have suggested that gal escape synthesis in lambda-induced lysogen results from transcription which initiates not only at PL but also at Pgal. The Pgal-promoted transcription may be a consequence, direct or indirect, of the concomitant replication of gal DNA.

Chloramphenicol↗

PubMed1979

Origin and binding specificity of protein(s) coded for by Mu prophages.

Crude extracts of bacteria lysogenic for temperature phage Mu contain proteins that retain specifically Mu DNA on nitrocellulose filters. The amount of binding protein is directly proportional to the number of Mu prophages per E. coli genome. Specificity of the binding reaction could be demonstrated by using heterologous DNAs as substrate and by a competition experiment. By using hybrid plasmids containing different amounts of the immunity end and extending to various degrees into MuDNA, it was found that the binding activity is coded for by the left 1,000 nucleotide-pair HindIII fragment. When using these hybrid plasmids as binding substrate, two different binding sites for the immunity product were detected. Joining of the MucI gene to the left lambda early promoter resulted in increased production of immunity protein at elevated temperature. A possible explanation for the relatively low amounts of immunity protein in all of the different strains studied is discussed.

Bacteriophage mu↗

PubMed1984

Frameshift mutagenesis of lambda prophage by 9-aminoacridine, proflavin and ICR-191.

The changes in DNA base sequence induced in the lambda cI gene in an E. coli lysogen have been determined following mutagenesis by three acridine derivatives: 9-aminoacridine and proflavin, which bind reversibly to DNA; and ICR-191, which attaches covalently to DNA through a half-mustard group. For all three derivatives, most mutations are +1 and -1 frameshifts in runs of adjacent G:C pairs. The specificity of mutagenesis at various sites is similar for all three compounds. Prophage in mutL host cells, deficient in mismatch repair, are much more susceptible to mutagenesis by 9-aminoacridine. The induced mutations are also frameshifts, and the site specificity is the same as in lysogens of wild type cells. Thus, additions or deletions of single bases can be corrected by the mismatch repair system, but mismatch repair does not play an important role in determining the sequence specificity of the mutational events.

Acridines↗

PubMed1975

E. coli K12 inf: a mutant deficient in prophage lambda induction and cell filamentation.

The bacterial mutant inf-3 (lambda) is not inducible and does not form filaments following thymine starvation. Lysogenic induction is neither produced by ultraviolet light (UV) nor promoted by tif-1. This phenotype is due to a mutation infA3 located between 60 and 73 min on the E. coli K12 map. The inf mutant is resistant to X-ray and UV irradiation, in contrast to all other known non-inducible bacterial mutants. It is Rec+ and able to perform host cell reactivation as well as UV-reactivation of phage lambda. After exposure to UV light, its DNA is degraded more than that of the parent and the resumption of DNA synthesis is delayed by 30 min; nevertheless, the cell survival is analogous to that of the parent. The inf mutant is also resistant to thymine starvation, for at least 3 hours. Wild type phage lambda forms clear plaques on a lawn of non-lysogenic inf bacteria; a corresponding low level of lysogenization is found. The capacity of inf bacteria to reproduce phages lambda, T4 or T6 is impaired. No gross defect in DNA transcription has been detected. Nevertheless, this mutant might have a slight alteration in the transcription process or in any other process involved in gene expression. This alteration might affect the regulation of DNA replication and cell division as well as prophage lambda induction.

Bacteriophage lambda↗

PubMed1984

Prophage induction in thermosensitive DNA mutants of Bacillus subtilis.

Incubation of thermosensitive dna mutants of Bacillus subtilis at the non-permissive temperature leads in some instances to induction of defective prophage PBSX and cell lysis. A clear distinction can be made between mutants affected in DNA replication at the growing point (extension mutants) and those unable to initiate new rounds of replication (initiation mutants). The former promote PBSX induction to a variable and mutation-specific extent, whereas the latter do not exhibit any signs of induction. Analysis of mutants carrying two dna mutations suggests that products of some dna genes involved in initiation and in extension are not essential for induction but can substantially amplify its extent. However, mitomycin C treatment of dna mutants which have completed their residual DNA synthesis leads to a PBSX induction essentially identical to that obtained by mitomycin C treatment of the wild-type strain, which precludes an essential role for any of the mutated proteins in this induction process. On the basis of our observations we propose that the induction signal is related to the number of blocked replication forks: the larger that number, the higher the proportion of induced cells within the population.

Bacillus subtilis↗

PubMed1984

Location by DNA sequence analysis of cop mutations affecting the number of plasmid copies of prophage P1.

The DNA sequence of six P1 cop mutants, which are altered in the control of copy number of the plasmid prophage, was compared to that of P1 wild type. Each cop mutant differs from the wild type by a single base substitution. All of these substitutions are located within a 400 base pair region of P1 DNA that also encodes rep, a gene whose product is required for P1 replication.

Amino Acid Sequence↗

PubMed1985

Prophage induction and filamentation in Bacillus thuringiensis caused by the genotoxic mycotoxin aflatoxin B1.

Cultures of the lysogenic strain of Bacillus thuringiensis var. tolworthi were made in the presence of various drugs. The determination of bacterial size and plaque forming units (by using an indicator strain of B. thuringiensis var. galleriae) as well as colony forming units were then performed. Treatment of lysogenic cells by aflatoxin B1: provokes the formation of elongated cells (filamentation); induces a pathway that leads to the induction of prophage. Results of the present study indicated that filament formation and bacteriophage induction are two commonplace effects that occur in virtually every member of this cellular population exposed to low doses of certain drugs such as aflatoxin B1 (10 micrograms/ml); all of which have in common the ability to produce damaging changes in DNA. The following findings support the hypothesis that error-prone repair mechanisms seem to be present in B. thuringiensis as in Escherichia coli.

Aflatoxin B1↗

PubMed1979

lambda-Prophage induction by furocoumarin photosensitization.

Furocoumarin photosensitization induces lambda-prophage from lysogenic Escherichia coli cells; this effect is clearly due to the photoreaction that furocoumarins give with DNA, and it appears connected with the formation of monoadducts rather than of diadducts (cross-links).

Coliphages↗

PubMed1996

phi 20, a temperate bacteriophage isolated from Bacillus anthracis exists as a plasmidial prophage.

This study describes the isolation of temperate B. anthracis phages, from 4 out of 20 B. anthracis strains screened, by use of the inducing agents mitomycin C and UV light. Phage phi 20 isolated from B. anthracis Sterne 34F2 (pXO1+ pXO2-) was shown to have double-stranded DNA of size 48756 bp and a restriction site map showing nine sites for enzymes BamHI, BglII, and SstI is included. The phi 20 genome was found to exist as a plasmidial prophage and the phage itself to have a polyhedral head of diameter 65 nm and tail 217 nm long and 15 nm wide.

Bacillus Phages↗

PubMed1997

Cloning with Mud-P22 hybrid prophages: mapping of IS200 elements on the chromosome of Salmonella typhimurium LT2.

Specific DNA fragments from the chromosome of Salmonella typhimurium LT2 were packaged in P22 capsids by induction of "locked-in" Mud-P22 hybrid prophages. High yields of the packaged DNA were obtained upon capsid disruption. DNA hybridization using a fragment of insertion sequence IS200 as probe permitted physical mapping of IS200 elements on the chromosome of S. typhimurium LT2 within +/- 1 centisome (CS). IS200 copies were found at the following locations: CS 24 (copy VI), CS 53 (copy V), CS 63 (copy I), CS 80 (copy II) and CS 93 (copy III). Copy IV, previously mapped near fliA (CS 42), was not included in our study.

Bacteriophage P22↗

PubMed1983

DNA damage, prophage induction and mutation by furazolidone.

Ultraviolet absorption data and thermal chromatography through hydroxyapatite (HAP) column revealed that furazolidone treatment of Vibrio cholerae cells produced more than 80% of DNA reversibly bihelical due to the formation of interstrand cross-links and the reaction obeyed a first order relation. Sensitivities of the Escherichia coli strains to the lethal action of the drug were in the order: AB 2480(uvr- rec-) greater than AB 2463(rec-) greater than AB 1886(uvr-) greater than AB 1157(repair proficient) or AB 4401(wild type). Furazolidone was 'Rec test' positive, produced dose-dependent prophage induction in E. coli cells and also dose-dependent streptomycin-resistance forward mutation in V. cholerae cells. The quantitative aspect and also the mode of furazolidone action on DNA were discussed.

DNA Repair↗

PubMed1989

Further evidence for photoinduced genotoxicity of dictamnine as shown by prophage induction.

Photobiological activity of dictamnine, a furoquinoline alkaloid, to induce lytic phage development in a lysogen of Escherichia coli was measured as a line of evidence for the photoinduced genotoxicity. Since dictamnine forms the monoadducts to DNA but not the diadducts (DNA cross-links) by photoirradiation, the photobiological activity was compared with that of a cross-linking agent 5-methoxypsoralen, a structural analog, on the basis of relative quantum yield. The activity of dictamnine with respect to both phage induction and photoinduced lethal activity was weaker than the psoralen derivative. Any lethal DNA damage including monoadducts and diadducts of 5-methoxypsoralen appeared to contribute to prophage induction at the same level of efficiency.

5-Methoxypsoralen↗

PubMed1989

Plasmid-partition functions of the P7 prophage.

The sequences responsible for the proper partition of the P7 plasmid prophage to daughter cells lie within a discrete block of non-similarity between P7 and its close relative P1. The DNA sequence of the P7 region was determined. A segment with near identity to the replication (rep) region of P1 is followed by sequences (P7 par) that are clearly related to but very divergent from the P1 partition region. Subcloning was used to define the ends of the functional P7 partition region. It begins with a transcription promoter followed by two large open reading frames, parA and parB, that overlap by a single base and are read in the same direction. The genes direct the synthesis of two proteins, P7 ParA and ParB, with apparent Mr of 44,000 and 37,000. Specific frameshift mutations were introduced into the two genes. Each mutation blocked plasmid partition and both were complemented when the P7 ParA and ParB proteins were supplied in trans. The amino acid sequences of the P7 proteins show strong similarities to the P1 ParA and ParB proteins. However, the DNA sequences of the P7 and P1 open reading frames are remarkably divergent, largely caused by variability at the third positions in the codons. Interspecific complementation tests showed that the P7 proteins are unable to complement P1 parA or parB mutants, and the P1 proteins fail to complement the P7 mutations. Downstream from the P7 parB open reading frame is a sequence that conserves 27 of the 34 base-pairs of the P1 partition site parS. Unlike the P1 parS site, the P7 equivalent does not contain as extensive an inverted repeat. The heptamer sequences that define ParB binding sites within P1 parS are represented in P7 but differ from it by one base. A related sequence that coincides with the secondary ParB binding site within the P1 incB sequences is present nearby. Other sequences within the P7 incB region are rather different from their P1 counterparts. The basis for the major differences in specificity of the P1 and P7 par components is discussed. Comparison of the P1 and P7 sequences, and the nature of the junctions between similar and different sequences, suggest that the phages could have evolved by the pickup of divergent cassettes by recombination.

Amino Acid Sequence↗

PubMed1978

Influence of the recF143 mutation of Escherichia coli K12 on prophage lambda induction.

Prophage lambda induction in a recF143 mutant of E. coli K12 was studied. The recF143 (lambda) lysogen was inducible by UV irradiation or treatment with mitomycin C. However, the time required for the onset of derepression brought about by these treatments was longer in the recF143 mutant than in rec+ strains, suggesting that the induction pathway was altered in the recF143 mutant. The recF143 (lambda) lysogen was induced at very low doses of UV irradiation or mitomycin C treatment. Moreover, the presence of the recF143 mutation increased the sensitivity to thermal induction of a tif strain.

Coliphages↗

PubMed1983

Studies on polylysogens containing lambda N-cI- prophages. II. Role of high multiplicities in lysogen formation by lambda N-cI- phage.

Results of the experiments presented in this paper show that lambda N-cI- phage can lysogenize a nonpermissive host Escherichia coli when it infects at very high multiplicities (around 100), and lambda N-cI-cII- and lambda cIII-N-cI- lysogenize poorly at similar high multiplicities. The latter two phages lysogenize with appreciable frequency when either lambda N-cI- or lambda int-cN-cI-cII- is used as helper. The phages, lambda N-cI-, lambda N-cI-cII-, and lambda cIII-N-cI- can lysogenize also at relatively low m.o.i. of 20 in presence of the above lambda int-c helper, and the lambda int-cN-cI-cII- phage alone forms converted lysogens at an m.o.i. as low as 12. All these results suggest that the establishment of prophage integration by lambda N-cI- is positively regulated, like lambda N+cI+ phage, by the cII/cIII-promoted expression of the int gene of lambda, and under the N- condition, high multiplicities are needed to provide optimum levels of cII and cIII products, especially the latter.

Bacteriophage lambda↗

PubMed1983

lambda-Transducing phages carrying transfer genes isolated from an abnormal prophage insertion into the traY gene of F.

A set of lambda-transducing phages carrying transfer (tra) genes has been isolated from an abnormal lysogen in which a lambda prophage was inserted into the traY gene of Flac. These have been characterized genetically for complementation of Flac tra and finP point mutants and for the presence of oriT. Studies of tra gene expression during lambda repression showed that tra genes on the transducing phages were expressed from the lambda PL promoter as well as from the transfer promoters when these were present. The molecular weights of the traM (14,000) and traJ (23,500) proteins were measured after infection of ultraviolet-irradiated cells with one of the phages, ED lambda 102, and overproduction of the traJ protein upon induction of an ED lambda 102 lysogen was demonstrated. A proportion of this traJ protein was located in the inner membrane and cytoplasmic fractions of the cell, the majority being in the outer membrane. Physical analysis of the DNA carried by the lambda tra phages by determination of the phage buoyant densities in CsCl, by restriction enzyme digestion and by electron microscope heteroduplex analysis, was used to define the DNA segments encoding the tra functions. Correlation of the physical and genetical data improved the positioning of the tra genes within the transfer region. These results were combined with new restriction enzyme cleavage data to construct an improved map of this region.

Attachment Sites, Microbiological↗

PubMed1987

The plasmid-maintenance functions of the P7 prophage.

The region responsible for the maintenance of the prophage of bacteriophage P7 as a stable, unit-copy plasmid was isolated in a lambda att vector which lysogenizes Escherichia coli as a stable unit-copy plasmid under the control of the P7 replication origin. The P7 plasmid-maintenance region was shown to consist of adjacent replication and partition regions capable of functioning independently. The isolated replication region could support plasmid maintenance but the resulting plasmids were highly unstable unless the partition region was also included. Stable composite plasmids were isolated containing the putative P7 partition region and the origin of replication of the unrelated plasmid F, indicating that P7 encoded an active partition mechanism. The replication regions of P7 and P1 were shown to be highly homologous but the partition regions of the two plasmids appear to be unrelated in sequence. The incompatibility determinants associated with the two replication regions showed the same specificity, whereas the partition-region incompatibility determinants were different, showing no cross-specificity.

Chromosome Deletion↗

PubMed1981

The influence of procarbazine (MIH) on the induction of prophage lambda in Escherichia coli K12 and toxic effects on Salmonella typhimurium.

Natulan R (MIH, procarbazine) was tested for its ability to induce prophage lambda in Escherichia coli GY5027. E. coli Gy4015 served as indicator strain. A weak phage-inducing effect was observed at concentrations from 2 to 12 mg/plate in presence of S9 prepared from rats. This effect was found not to be due to the formation of hydrogen peroxide. It was confirmed that, even at the same high concentrations, no mutagenic effect can be detected with the Ames test in strains TA98 and TA100 of S. typhimurium. However, a toxic effect was observed in presence of S9 in S. typhimurium.

Bacteriophage lambda↗