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At least 73 records · Page 4Linked to original sources
PubMed1967

Effects of mitomycin C and thymidine deprivation on lysogenic and sensitive strains of Bacillus megaterium.

A triple auxotroph of Bacillus megaterium strain KM was lysogenized with a phage suspension from B. megaterium 899a. The lysogenic and phage-sensitive derivatives of KM were found to die at the same exponential rate during thymineless incubation, despite the fact that the lysogenic strain became induced. The lysogenic strain was also induced by mitomycin C, and died at an exponential rate which was approximately twice that of the sensitive strain. With both strains, the lethality of mitomycin C was the same in the presence and absence of thymidine; thymidine was required for maximal phage production. Mitomycin C preferentially inhibited deoxyribonucleic acid (DNA) synthesis of both strains for the first 60 min. The (DNA) synthetic ability of the lysogenic strain was subsequently restored, due to phage production. Since there was no evidence that sensitive strains of KM contained other inducible elements (prophage or probacteriocins), it is concluded that both thymineless death and mitomycin C death can occur via mechanisms not involving induction.

Bacillus megaterium↗
PubMed1973

DNA-mediated prophage induction in Bacillus subtilis lysogenic for phi 105c4.

Prophage was induced when strains of Bacillus subtilis 168 lysogenic for phi105c4 were grown to competence and exposed to specific bacterial DNAs. The time course of phage production was similar to that observed for mitomycin C induction of wild-type prophage. Induction was directly dependent upon DNA concentration up to levels which were saturating for the transformation of bacterial auxotrophic markers. The extent of induction varied with the source of DNA. The burst of phage induced by DNA isolated from a W23 strain of B. subtilis was fivefold less than that induced by DNA from B. subtilis 168 strains, while B. licheniformis DNA was completely inactive. This order of inducing activity was correlated with the ability of the respective DNAs to transform auxotrophic markers carried by one of the phi105c4 lysogens. Differences in inducing activity also were observed for different forms of phi105 DNA. The DNAs isolated from phi105 phage particles and phi105c4 lysogens were inactive, whereas DNA from cells lysogenized by wild-type phi105 induced a burst of phage. When tested for transforming activity, however, both phi105c4 and phi105 lysogen DNAs were equally effective. An induction mechanism which involves recombination at the prophage insertion site is proposed to explain these differences.

Bacillus subtilis↗
PubMed1977

Increased reproductive fitness of Escherichia coli lambda lysogens.

Lambda lysogens of Escherichia coli reproduce more rapidly than nonlysogens during aerobic growth in glucose-limited chemostats. If the environment is changed to anaerobic growth, the situation is reversed, and the lysogen reproduces more slowly than the nonlysogen. Based on a tetrazolium dye assay, the increased fitness of the lambda lysogen during aerobic growth seems to result from a continued high metabolic rate as glucose becomes limiting, whereas the metabolic rate of the nonlysogen declines. The lambda rex gene is required for the growth advantage of lysogens since lack of rex function causes lambda lysogens to lose their reproductive advantage over nonlysogens.

Aerobiosis↗
PubMed1977

Reproductive fitness of P1, P2, and Mu lysogens of Escherichia coli.

P1, P2, and Mu lysogens of Escherichia coli reproduce more rapidly than nonlysogens during aerobic growth in glucose-limited chemostats. Thus, prophage-containing stains of E. coli are reproductively more fit than the corresponding nonlysogens. If mixed populations are grown by serial dilution under conditions in which growth is not limited, both the lysogen and nonlysogen manifest identical growth rates. The increased fitness of the lysogens in glucose-limited chemostats correlates with a higher metabolic activity of the lysogen as compared with the nonlysogen during glucose exhaustion. We propose that P1, P2, Mu, and lambda prophage all confer an evolutionarily significant reproductive growth advantage to E. coli lysogenic strains.

Aerobiosis↗
PubMed1988

Characterization of a spontaneously segregating Cf16-v1 lysogen of Xanthomonas campestris pv. citri.

Filamentous phage Cf16 undergoes a unique neolysogenic infectious cycle in Xanthomonas campestris pv. citri and generates stable lysogens. In contrast, we have isolated a distinctive unstable lysogen, designated LW. This new lysogen segregated spontaneously into three nonparental types, each with a unique combination of colony morphology, phage-producing capacity, and phage genome content. In a given population of LW lysogens the segregation frequency of these types varied randomly with drastic fluctuations from experiment to experiment. Heat and UV treatment failed to increase the segregation frequency with a magnitude matching the sporadic intrinsic fluctuations. The characteristics of an LW lysogen were transmitted through the phage it released. Designated as Cf16-v1, this phage, which produced clear instead of turbid plaques as its progenitor Cf16, was exceedingly unstable in the host cell. Only 4% of the infected cells, rather than 95% as in the case of Cf16, retained the phage genome and completed the neolysogenization process. The prophage integration site on the host chromosome, however, appeared to be the same for both phages.

Bacteriophages↗
PubMed1984

[Stimulation of the lysogenization of Pseudomonas aeruginosa cells by phage transposon B39 induced by plasmid Rms163].

The influence of Rms163 plasmid on lysogenization of Pseudomonas aeruginosa cells by B39 phage was studied. Plasmid Rms163 was shown to increase the frequency of lysogenization of PAO1 cells 7-8 times. C-mutants of B39 phage were isolated. According to complementation test, c-mutants were distributed into two groups--cI and cII/III. The product of cI is essential for establishment and maintenance of lysogenic state, cII/cIII product being only necessary for establishment of lysogenization. The mutants with special characteristics were isolated: B39cx1 phage carries a mutation which seems to be located on a regulatory site essential for establishment of lysogenic state. The region of the B39 genome responsible for interaction with Rms163 plasmid was mapped. Possible mechanisms of Rms163 plasmid interference with transposable B39 phage are discussed.

Bacteriophages↗
PubMed1976

[Lysogenic clones of wild-type plague bacteria and characteristics of the phages produced by them].

Comparative population analysis of 3 lysogenic clones of plague bacteria of wild type by lysogenic properties demonstrated that they failed to show any difference from one another by immunity to homolgous and heterologous phages, but differed by the number of cells capable of producing the phage spontaneously. Lysogenic properties were transmitted by heredity both after the ten-fold passage in the presence of a homologous antiphage serum and after a 10-fold colning. Phages produced by the wild lysogenic clones of plague bacteria were capable of provoking lysogenization of bacteria sensitive to it, they were serologically affiliated and differed by the range of action on plaque and pseudotuberculosis bacteria sensitive to it.

Bacteriophages↗
PubMed1979

X-ray sensitivity of Escherichia coli lysogenic for bacteriophage P2.

Strains of Escherichia coli C or K lysogenic for the non-inducible phage P2 show a lower survival following X-ray irradiation as compared to nonlysogenic strains. This difference in X-ray sensitivity is not accompanied by a significant difference in X-ray induced mutability. The capacity of X-irradiated P2 lysogens to multiply any of a number of unirradiated infecting phages is severely impaired. These effects of X-ray treatment can be most simply explained as a consequence of the fact that protein and RNA syntheses are strongly inhibited in P2 lysogens after X-irradiation. All the above events specifically occurring in X-rayed P2 lysogens are dependent on the P2 gene old.

Bacterial Proteins↗
PubMed1982

Phenotypic variations in re-lysogenization of Bacillus licheniformis with temperate phage.

A bacitracin-producing strain Bacillus licheniformis ATCC 10716 harbors two types of inducible phages (LP52 and DLP 10716). 156 strains re-lysogenized with phage LP52 were independently isolated from a cured strain UM12 of B. licheniformis. Those strains were divided into 12 groups based on colony morphology and pigment production. Some of the re-lysogenized strains grew faster than UM12 and others produced more bacitracin than the cured strain. For example, the production of bacitracin by one of the re-lysogenized strains, L89, was enhanced by about 70% in comparison with UM12. The phenotypic variations observed with re-lysogenized strains might be due to the re-insertion of the phage genome at different sites of the chromosome in addition to the pleiotropic effect assumed.

Bacillus↗
PubMed1992

Bioluminescence detection system of mutagen using firefly luciferase genes introduced in Escherichia coli lysogenic strain.

A rapid and convenient microbial sensing system for mutagens was developed based upon the induction of prophage from Escherichia coli lysogenic strain and bioluminescence. The system consisted of lysogenic E. coli encoding firefly luciferase genes and a photodetection system. Measurement of mutagen mitomycin C was achieved by measuring the luminescence intensity emitted from E. coli lysogenic strain for the recombinant phage in the presence of luminescence substrates. Approximately 1 h after addition of mitomycin C, the luminescence began to be observed, and 3 h after, it attained a level of 2 times greater than that of 1 h. Irradiation with ultraviolet light also produced light based on induction of phage from the E. coli lysogenic strain for the recombinant phage. On the other hand, when nonmutagenic toxic compounds like sodium azide were added to the reaction medium, luminescence was not observed. Mitomycin C could be detected within 1 h with this sensing system, at concentrations down to 10(2) ng/assay.

Bacteriophage lambda↗
PubMed1997

Host regulation of lysogenic decision in bacteriophage lambda: transmembrane modulation of FtsH (HflB), the cII degrading protease, by HflKC (HflA).

The cII gene product of bacteriophage lambda is unstable and required for the establishment of lysogenization. Its intracellular amount is important for the decision between lytic growth and lysogenization. Two genetic loci of Escherichia coli are crucial for these commitments of infecting lambda genome. One of them, hflA encodes the HflKC membrane protein complex, which has been believed to be a protease degrading the cII protein. However, both its absence and overproduction stabilized cII in vivo and the proposed serine protease-like sequence motif in HflC was dispensable for the lysogenization control. Moreover, the HflKC protein was found to reside on the periplasmic side of the plasma membrane. In contrast, the other host gene, ftsH (hflB) encoding an integral membrane ATPase/protease, is positively required for degradation of cII, since loss of its function stabilized cII and its overexpression accelerated the cII degradation. In vitro, purified FtsH catalyzed ATP-dependent proteolysis of cII and HflKC antagonized the FtsH action. These results, together with our previous finding that FtsH and HflKC form a complex, suggest that FtsH is the cII degrading protease and HflKC is a modulator of the FtsH function. We propose that this transmembrane modulation differentiates the FtsH actions to different substrate proteins such as the membrane-bound SecY protein and the cytosolic cII protein. This study necessitates a revision of the prevailing view about the host control over lambda lysogenic decision.

ATP-Dependent Proteases↗
PubMed1952

The B. mycoides N host-virus system. I. Differences in appearance and "rate of growth" of the lysogenic and parent indicator strains.

There were differences in the way the lysogenic strain N of B. mycoides and the parent indicator strain grew on nutrient agar and in nutrient broth. 1. On agar, the indicator culture traveled more quickly over the agar surface than the phage-carrying strain; the total extent of spread was greater. 2. In broth, the indicator strain grew diffusely throughout the liquid, the lysogenic cells in clumps. The virus-infected strain appeared to grow more slowly. This may reflect (a) the effect of aggregation on the generation time of the lysogenic strain, (b) an active lytic process in the lysogenic population which is further enhanced by the effect of clump formation on the environment of the cell.

Bacillus↗
PubMed1952

The B. mycoides N host-virus system. III. Release of phage from the lysogenic strain.

Experiments were performed to determine the mechanism of release of phage from the lysogenic strain of B. mycoides N. The results suggest that qualitatively the same situation obtains as in the phage-carrying cultures of B. megatherium 899 and E. coli Li; i.e., the population consists of two kinds of cells: "lysogènes potentiels" and "producteurs." Quantitatively, however, there are more "producers" in a broth culture of the lysogenic B. mycoides N, at least curing the first 4 to 8 hours after cells have been suspended in fresh medium, suggesting that the interaction between host and parasite is one in which the balance is easily swung in favor of the virus. These conclusions are based upon the following lines of evidence: (1) the slow "growth rate" of the lysogenic culture, (2) the fact that the colony count falls far below the plaque count or the filament count (which correspond) for a well washed suspension, (3) the increase in phage output in a large number of tubes, each containing a small number of lysogenic cells, after a few hours' incubation in nutrient broth at 30 degrees C.

Bacteria↗
PubMed1986

Phage-typing patterns and lysogenicity of methicillin-resistant strains of Staphylococcus aureus from Sydney, Australia, 1965-85.

Methicillin-resistant strains of Staphylococcus aureus isolated at the Royal Prince Alfred Hospital since 1965 were differentiated by phage-typing and by their lysogenic status. Most of these strains were isolated during two periods, 1965-72 and 1976-85. Nearly all of the strains isolated in the first period had one of four phage-typing patterns. Strains with each typing pattern carried two prophages; these eight phages were all different, as characterised by serological grouping and lytic spectrum. Lysogenisation of the non-lysogenic strain 1489 with each of these phages narrowed its phage-typing pattern; the typing pattern of the double lysogens was generally similar to and occasionally identical with that of the host strain that had yielded the pair of phages. In the second period, strains with one of five other phage-typing patterns predominated. Representatives of each of these carried the lysogenic phage C. The first methicillin-resistant strain carrying this phage had been isolated in 1974. The current methicillin-resistant S. aureus strains thus appear to form a distinct group that can be differentiated from those seen in earlier years.

Australia↗
PubMed1995

Presence of lysogenic phage in the outbreak strains of Vibrio cholerae O139.

Four outbreak strains of Vibrio cholerae O139 from endemic areas of India and Bangladesh were found to carry lysogenic phage(s). All of these phage(s) produced turbid plaques characteristic of lysogeny on V. cholerae MAK 757 (El Tor, Ogawa) cells as well as on their VcA-1 lysogens but were unable to infect V. cholerae 154 (classical) cells, the universal host for all classical phages. Colonies in the turbid plaques were O139 lysogens and these developed an auxotrophic requirement, mainly for purines suggesting the integration of the prophage into the host chromosome. The immunity profile of the O139 phage(s) was similar to that of phage alpha but differed in the sensitivity of the phage lysogen of V. cholerae MAK 757 to subsequent infection by phage beta.

Bacteriophages↗
PubMed1975

Induction of phage production in the lysogenic Escherichia coli by hydroxyurea.

1) Hydroxyurea, a reversible DNA synthesis inhibitor, was used to study the mechanism of prophage lambda induction in Escherichia coli K12. Induction of prophage was judged on two criteria: increase of phage-producing cells and loss of colony-forming ability of the cells. 2) Hydroxyurea induced an increase of phage-producing cells only in lysogenic strains known to be inducible with ultraviolet irradiation for prophage development and not in strains such as E. coli K12 (lambdaind-) or E. coli K12 recA (lambda+). 3) When protein synthesis was inhibited, hydroxyurea did not increase phage-producing cells of lysogenic strains; it showed a bacteriocidal effect on lysogenic recA+ strains, but not on nonlysogenic strains. 4) The sensitivity of E. coli K12 recA to hydroxyurea was independent of whether or not the cells were lysogenic. 5) From the results it is suggested that certain steps leading to loss of colony-forming ability (i.e. prophage induction) do not require de novo protein synthesis but require the presence of the host recA+ gene.

Bacterial Proteins↗
PubMed1993

Lysogenic phage in Salmonella enterica serovar heidelberg (Salmonella Heidelberg): implications for organism tracing.

A phage typing system using a group of 11 closely related phage (as judged by Southern analysis and restriction fragment length polymorphism analysis) was able to distinguish at least six phage types in Salmonella heidelberg of human and animal origin. Restriction fragment length polymorphism analysis using cosmid probes from S. heidelberg confirmed that most S. heidelberg isolates belong to a single 'clonal' group. Southern analysis using DNA isolated from each of the testing phage group showed that phage types 4, 5 and 6 carry closely related endogenous or lysogenic phage. Induction of a lysogenic phage Hlp-4 (Heidelberg lysogenic phage) from type 4 could become lysogenic and convert phage types 1 and 3 to phage type 4 and phage type 5 to a non-typable phenotype.

Bacteriophage Typing↗
PubMed1979

Conditions for induction of bacteriophage from lysogenic Bacillus megaterium with aflatoxin B1.

The present study was conducted to determine whether or not aflatoxin B1 was an effective inducing agent for lysogenic bacteria and to characterize some of the parameters involved in induction. A lysogenic strain of Bacillus megaterium (NRRL-B-3695) and an indicator strain of this species (NRRL-B-3694) were used. Cultures of the lysogenic strain were incubated for various periods of time in the presence of aflatoxin B1. Plaque-forming units as well as colony-forming units were then determined. Results of the present study indicated that bacteriophage lysogenizing B. megaterium could be induced with aflatoxin B1. The optimum concentration for induction was 25 micrograms of toxin per ml of early-log-phase culture. Evidence suggested that: (i) higher concentrations of aflatoxin B1 formed hydrophobic complexes which would not efficiently induce B. megaterium; (ii) the toxic effect of aflatoxin B1 severely limited the number of cells which could be induced prior to killing action of the toxin; and (iii) concentrations less than 25 micrograms of aflatoxin B1 per ml were not efficient inducers of bacteriophage production nor did they demonstrate the toxic effect observed at higher concentrations.

Aflatoxins↗