Lysogenic Strains Research Articles

Lysogenicity and prophage type of the strains of Vibrio cholerae O-1 isolated mainly from the natural environment.

Attention has recently been given to the increasingly frequent detection of atypical Vibrio cholerae O-1 in the natural environments throughout the world. Lysogenicity of V. cholerae O-1, mainly isolated from environmental sources in nine areas, including the United States, was studied by electron microscopy and a cross-lysis test between bacteria and the culture supernatants. A total of 38 strains isolated in Texas in 1973 and in Louisiana in 1978 were lysogenic, whereas there were no lysogenic strains among those isolated in Louisiana in 1979. Because these phages were identical in terms of serology and host range, the phage in them was named T-L phage. T-L phage differed in host range from the k type phage in the epidemic strain of the seventh cholera pandemic. Although the T-L phage was neutralized by antiserum to the k type phage and vice versa, the two phage types were not serologically identical. By a prophage typing method, strains of V. cholerae O-1 isolated from the environment in Guam, Bangladesh, and Japan were classified as either of the Celebes type (epidemic strain) or the Classic-Ubon type. All strains isolated in Brazil, the Chesapeake Bay, and England were nonlysogenic and classified as Classic-Ubon type.

Evaluation of the Escherichia coli K12 inductest for detection of potential chemical carcinogens

46 chemicals of diverse classes and structures, including 30 known animal carcinogens, were evaluated for prophage-inducing ability using the Escherichia coli inductest with lysogenic strain GY5027 envA − uvrB − and indicator strain GY4015 amp R . The inductest detected 9 of 30 known carcinogens as genotoxic agents, including 3 polycyclic hydrocarbons, 2 aflatoxins, and 2 antitumor antimicrobials. Among the 21 carcinogens ineffective as prophage inducers were 3 aromatic amines (other than 2-aminoanthracene), 3 azo-aminoazo compounds, 2 methanesulfonates, and 2 nitro aromatics. In contrast, 18 and 17 of the 30 animal carcinogens were detected as genotoxic agents in the Salmonella/Ames test and E. coli WP2/WP100 rec assay, respectively. The threshold sensitivity of the inductest was less than that of the Salmonella/Ames test for chemicals genotoxic in both tests. The ineffectiveness of the inductest as a routine test for detecting potential chemical carcinogens may be related to the nature of the DNA damage lesions formed by various genotoxic agents.

UV-induction of SOS responses in Staphylococcus epidermidis: characteristics of the process.

Abstract— Lysogenic induction, Weigle reactivation (WR) and Weigle mutagenesis (WM) induced by UV radiation were studied using the wild type Staphylococcus epidermidis W5 and its u> phage. The difference in UV sensitivity between the lysogenic and non‐lysogenic strains of S. epidermidis is extremely large when compared with wild type non‐lysogenic and lysogenic strains of Escherichia coli. The kinetics of prophage liberation by the lysogenic culture of 5. epidermidis are faster than those described for E. coli. The UV‐fluences which result in the maximum lysogenic induction, WR and WM are much lower than those described for E. coli. The maximum WR and WM are obtained immediately after the irradiation (within the 15 min allowed for phage adsorption). We suggest that in S. epidermidis the basal level of RecA protein can promote the efficient induction of SOS functions.

The lon gene and photoprotection in Escherichia coli K-12.

Abstract— Photoprotection i. e. the increased resistance of the cells preilluminated with near ultraviolet light (300–380 nm) to the lethal action of 254 nm radiations is observed in wild‐type Escherichia coli B cells (which exhibits the Fil phenotype) but requires either an integrated prophage or a recA mutation to be detected in E. coli K12 strains. Here we have demonstrated that significant photoprotection occurs in an E. coli K12 recA+ cell containing the Ion allele which is responsible for filamentous growth (Fil phenotype) after 254 nm irradiation. The Fil phenotype can be suppressed by the sfiA of sfiB suppressor genes. Since the E. coli K12 recA+Ion sfiB strain exhibits no more photoprotection, these data support the conclusion that in Ion strains photoprotection is due to the abolition of the 254 nm induced filamentation by the near ultraviolet treatment. In addition, we show here that near ultraviolet illumination of the cells leads to a severe restriction of the bulk protein synthesis, as well as of the inducibility of β‐galactosidase and tryptophanase. These effects are observed only in nuv+ cells that contains 4‐thiouridine the chromophore responsible for photoprotection. We propose that in Ion (lysogenic) strains, photoprotection is due to prevention of the SOS response. During the growth lag, the low residual level of protein synthesis does not allow the induction of the SOS response and accordingly prevents filamentation (the lytic cycle). Concomitantly the SOS triggering signals are eliminated via DNA repair.

Conditionally replicating plasmid vectors that can integrate into the Klebsiella pneumoniae chromosome via bacteriophage P4 site-specific recombination.

P4 is a satellite phage of P2 and is dependent on phage P2 gene products for virion assembly and cell lysis. Previously, we showed that a virulent mutant of phage P4 (P4 vir1) could be used as a multicopy, autonomously replicating plasmid vector in Escherichia coli and Klebsiella pneumoniae in the absence of the P2 helper. In addition to establishing lysogeny as a self-replicating plasmid, it has been shown that P4 can also lysogenize E. coli via site-specific integration into the host chromosome. In this study, we show that P4 also integrates into the K. pneumoniae chromosome at a specific site. In contrast to that in E. coli, however, site-specific integration in K. pneumoniae does not require the int gene of P4. We utilized the alternative modes of P4 lysogenization (plasmid replication or integration) to construct cloning vectors derived from P4 vir1 that could exist in either lysogenic mode, depending on the host strain used. These vectors carry an amber mutation in the DNA primase gene alpha, which blocks DNA replication in an Su- host and allows the selection of lysogenic strains with integrated prophages. In contrast, these vectors can be propagated as plasmids in an Su+ host where replication is allowed. To demonstrate the utility of this type of vector, we show that certain nitrogen fixation (nif) genes of K. pneumoniae, which otherwise inhibit nif gene expression when present on multicopy plasmids, do not exhibit inhibitory effects when introduced as merodiploids via P4 site-specific integration.

Absence of functional RNA encoded by a silent chromosome in non-complementing diploids obtained from protoplast fusion in Bacillus subtilis.

The molecular basis for lack of phenotypic expression of one chromosome in Bacillus subtilis non-complementing diploid clones (Ncd cells) was investigated. Correlations between chromosomal inactivation and absence of functional transcripts were determined with wild-type prophage phi 105 or a thermoinducible mutant phi 105 cts23, on either the expressed or the silent chromosome. It appears that no significant amount of phage mRNA is detectable in Ncd cells carrying the prophage in the inactive chromosome. However, phi 105 mRNA represents 0.23% of total cellular mRNA in an Ncd strain with the prophage in the expressed chromosome and 0.28% in the parental lysogenic strain. The lack of an mRNA repressor of phi 105 prophage from the silent chromosome was confirmed by the absence of repressor activity in Ncd clones with a temperature sensitive mutant phi 105 located in the silent chromosome. After heat induction, no phage production was observed. As expected these clones do not exhibit phi 105 immunity when superinfected with the same phage. The combined data of the present and previous work suggest that control of phenotypic suppression of Ncd strains should, at the transcription level, involve a different DNA tertiary organisation in one of the two chromosomes.

Phage-induction from lysogenic strains of Pseudomonas syringae pv. mori by the extract from mulberry leaves.

Phage-induction from lysogenic strains of Pseudomonas syringae pv. mori by the extract from mulberry leaves.

SEROLOGICAL GROUPING OF TEMPERATE PHAGES ISOLATEDFROM STAPHYLOCOCCUS AUREUS

According to the serological grouping of temperate phages isolated from clinical isolates, many strains of them were a doubly lysogenic strain carring serotype A and B. Staphylococcus aureus MS3878 was also a doubly lysogenic strain carring serotype A and B. Phages induced from Staphylococcus aureus MS3878 were purified followed by density gradient centrifugation in CsCl, and these phages were used for transduction analysis. The transduction frequency of the nonconjugative drug resistance plasmids rms6 and rms7 with phage serotype A was about 10 -10, but that with phage serotype B was 10 -5 to 10 -7.

Sensitivity of Escherichia coli acrA mutants to psoralen plus near-ultraviolet radiation

The sensitivity to psoralen plus near-ultraviolet radiation (PUVA) was compared in a pair of E. coli strains differing at the acrA locus. Survival was determined for both bacteria and phage lambda. AcrA mutant cells were 40 times more sensitive than wild type to the lethal effect of PUVA. Free lambda phage exposed to PUVA survived as well when plated on acrA mutants as on wild type. In contrast, prophage lambda CI857 ind carried in lysogenic acrA strains was hypersensitive to PUVA. The enhanced sensitivity of bacterial and lambda DNA, when inside acrA cells, was paralleled by an increased photobinding of radiolabelled psoralens in the mutant. Binding was increased specifically to DNA rather than to nucleic acids in general. The difference in psoralen-binding ability determined by the acrA gene persisted after permeabilizing treatment of the cells. The results suggest that the acrA mutation causes an alteration specifically in the environment of the cellular DNA so as to allow increased intercalation and photobinding of psoralens.

Accessory replicons of species of Salmonella and Shigella.

Shigella and Salmonella strains isolated from clinical samples were examined. Out of 42 Shigella strains tested, 17 (40%) were found to be colicinogenic and another 3 were lysogenic. All three lysogens yielded a phage antigenically homologous to coliphage P2. Out of 30 strains tested, only 1 was found to be resistant to both neomycin and sulfamethoxazole. Out of 48 strains of Salmonella tested for drug resistance, only 2 showed multiple drug resistance. In contrast to Shigella isolates, the Salmonella isolates were infrequently (approximately 5%) bacteriocinogenic. The frequency of lysogeny in Salmonella strains was found to be 6% when tested on Salmonella typhimurium LT2, but by using a set of five indicators belonging to species Salmonella potsdam, Salmonella mbadanka, Salmonella dublin, Salmonella london, and Salmonella wandsworth, 50% of the strains were shown to be lysogenic. Salmonella phages related to P22 were recoverable from Salmonella saintpaul, Salmonella indiana, and Salmonella heidelberg. Some isolates of S. typhimurium yielded a temperature-sensitive and P22-heterologous phage which was found to be a more efficient transducer of bacterial genetic markers than P22. EcoRI-generated fragments of the DNA of some phages permitted the establishment of a clonal descent for some of the wild-type lysogenic bacterial strains. This last observation points out the potential usefulness of prophages as epidemiological markers.

Polarity suppression by the Q gene product of bacteriophage λ

The late genes of bacteriophage λ are positively regulated by the phage Q protein. It has been proposed that Q stimulates late gene transcription by acting as an antiterminator of transcription, allowing extension of the 6 S transcript into the late genes. We have examined the ability of Q to act as an antiterminator by analysis of lysogenic strains in which the bacterial gal operon is oriented in the same direction as the prophage late genes. This orientation is achieved in lysogens carrying a λgt-C′ prophage, which has an inversion of the region containing the phage att site. In such λgt-C′ lysogens, synthesis of the galK product (galactokinase) is induced by the phage Q protein. Galactokinase expression is likewise induced by Q in strains carrying polar mutations in the gal operon ( ochre and amber nonsense mutations and IS1 and IS2 insertion elements). Q-dependent relief of polarity does not require the phage N protein, early promoters, or any phage proteins under Q control and does not require replication of the prophage DNA. Q protein thus appears to be sufficient to suppress polarity and hence is a late gene analogue of the early gene transcription antiterminator, N protein.

Konversion des serovars von Bordetella parapertussis durch lysogenie, erzeugt mit pertussisphagen

Bacteriophages from Bordetella pertussis were titrated on the indicator strain B. parapertussis 17903 by using standard soft agar techniques. Secondary growth, occassionally observed in some phage plaques, was isolated and transferred onto selective media. Judging from growth on these special media and microscopic examination the isolated clones consisted entirely of Bordetellae. Determination of the agglutinogen pattern of 160 of these clones revealed that 88% contained agglutinogen 1; 87.5% agglutinogen 14, and 80.1% agglutinogen 12 (Table 13). However, none of the strains expressed the agglutinogen pattern of either the phage donor or the recipient strain. The isolated clones were lysogenic as demonstrated by phage production and immunity against superinfection (95% of the clones). — Absorption of the monospecific antisera with whole cells from lysogenic strains resulted in a drastic decrease or even complete loss of specific antibodies towards those antigens identified by slide agglutination reactions (Table 4). Cross absorption experiments with antisera against B. pertussis, B. parapertussis and strain 731/7 and various strains of the genus Bordetella and with a number of lysogenic strains showing various agglutination patterns allowed the conclusion that the latter ones were serologically related to B. pertussis. The lysogenic strains completely absorbed antibodies against B. bronchiseptica, and those strains that carried the agglutinogen 14 also absorbed antibodies against B. parapertussis (Table 5).In conclusion, these results support the necessity to revise the subdivision of the genus Bordetella into three species. A change of B. parapertussis to B. pertussis within the epidemiological process is considered.

Restriction endonuclease map of the nontoxigenic corynephage gamma c and its relationship to the toxigenic corynephage beta c.

Clear-plaque-forming mutant gamma tox- corynephages were isolated independently from nontoxigenic lysogenic Corynebacterium diphtheriae strains C7s(gamma tox-) and C4(gamma tox-). A physical map was constructed by using restriction endonucleases BamHI, EcoRI, HindIII, and KpnI. A comparison of nontoxigenic gamma c with toxigenic corynephage beta c revealed large areas of homology, including common regions for cohesive ends (cos) and attachment sites (att). Localization of the att sites on the beta prophage and correlation of the physical and genetic maps defined the orientation of the diphtheria tox operon. Diphtheria tox sequence homologies were mapped on gamma c by hybridizing 32P-labeled diphtheria tox mRNA to restriction fragments of gamma c DNA. Two regions of heterogeneity between phages beta c and gamma c were localized and these regions accounted for the 3-kilobase larger molecular size of gamma c compared with beta c. One change occurs near the tox promoter and may explain the nontoxigenic phenotype of corynephage gamma tox-.

Phage influence on the synthesis of extracellular toxins in group A streptococci.

Phage conversion of group A streptococci to produce streptococcal exotoxins was shown to occur more widely than has been previously reported. Toxigenic conversion was found in 19 newly constructed lysogenic and pseudolysogenic strains resulting in synthesis of exotoxin types A and B. Conversion was accomplished by a positive conversion effector, which was a phage characteristic expressed by the prophage and vegetatively reproducing phage. Exotoxin production was determined by the rabbit skin test and by countercurrent immunoelectrophoresis with type-specific antisera. New lysogens and pseudolysogens were constructed with strains which failed to produce at least one exotoxin type. Phages were obtained from toxigenic strains isolated from cases of scarlet fever. Conversions were consistent and repeatable; loss of the recently introduced phage was accompanied by loss of the newly acquired toxin productivity. Conversion resulted in production of additional exotoxin type or types and never affected existing toxin synthesis. Converting phages were characterized by electron microscopy and negatively stained preparations and were all found to be of morphological class B1. All phage nucleic acid was double-stranded DNA. Though similar in structure, each converting phage had a different host range, and the nine new converting phages identified here did not react with antiserum prepared against the originally reported converting phage.

Isolation of bacteriophages for typing Staphylococcus intermedius isolated from pigeons

Attempts to isolate phages for typing Staphylococcus intermedius isolated from pigeons were made. Five phages were isolated from the lysogenic strains and the nostrils of pigeons, and were used for typing 50 strains isolated from pigeons in Japan, Belgium and Czechoslovakia. Thirty-one (62.0%) of the 50 strains were typed at either routine test dilution (RTD) or 100 × RTD into 8 phage patterns. A total of 122 strains of S. intermedius isolated from dogs, horses, mink and foxes were subjected to phage typing with pigeon phages, with the result that 10 (8.2%) of the 122 strains were typable. S. aureus and S. epidermidis, 59 and 58 strains, respectively, were resistant to lysis due to the pigeon phages. The experimental phages were considerably specific for S. intermedius isolated from pigeons.

Isolation of bacteriophages from Listeria monocytogenes serovar 5 and Listeria innocua

11 new bacteriophages, 3 from Listeria monocytogenes serovar 5 and 8 from Listeria innocua were isolated from lysogenic strains without induction. Phagovar determinations were carried out with these phages and 12 other isolated from L. monocytogenes serovars 1/2 and 4b. 76% of the 142 strains from different serovars tested gave a lytic pattern. The new phage set increased the percentage of determinable L. innocua strains to 61.7%. Different phage patterns underline the distinction between L. monocytogenes and L. innocua. L. monocytogenes serovar 5 is characterized by its great sensibility to many phages from lysogenic strains of various serovars.

Lysogenic Strains of Lactic Acid Streptococci and Lytic Spectra of Their Temperate Bacteriophages

A total of 113 strains of mesophilic strains lactic streptococci of the species Streptococcus lactis, S. lactis subsp. diacetilactis, and S. cremoris, chosen from 291 strains that had been previously classified into six groups on the basis of their sensitivity to 132 virulent phages, were subjected to induction with mitomycin C. Among these strains, 43% produced phages capable of forming plaques of lysis on an indicator strain either spontaneously or after induction. There was a close correlation between the lytic spectra of temperate and virulent phages. Among the strains studied, 25% were shown to be indicator strains. These results emphasized the high probability of development of temperate phages in a starter culture containing mesophilic lactic streptococci and therefore their importance as a cause of accidents in cheese making.

Lysogenicity and phage typing of Yersinia enterocolitica isolated in Japan.

Lysogenic strains were demonstrated by ultraviolet rays irradiation for the 292 strains of typical Yersinia enterocolitica and 57 strains of atypical Y. enterocolitica isolated in Japan. Wholly strains of serovar 3 and 5B were lysogenic. Strains of serovar 9 were non-lysogenic. Of 57 strains of atypical Y. enterocolitica, 5 were found to be true lysogenic ones. No lysogenicity was recognized on any strains of serovar 3 when Y. enterocolitica isolated in Japan was used as indicator strain, whereas liberation of phages was confirmed by strain Ye 3827 using as indicator strain. Phages derived from strains of serovar 5B were detectable with any strains of serovar 3 as indicator strain. Phage activity and liberation of phages were demonstrated at an incubation temperature of 25°C, but not at 37°C. All strains of serovar 3 were susceptible to phages I to XII except the phage XII.

Spontaneous release of mycophages from lysogenic bovine strains

Mycophages were successfully isolated from lysogenic bovine strains without previous exposure to physical or chemical agents. These mycophages were exposed to 53 mycobacterial strains using ATCC 607 as an indicator strain. These strains included rapidly growing strains, human, bovine, avian, murine and BCG strains of different geographical origin. Mycophages PM/90/69 produced lysis of human bovine, murine, BCG strains and most of the rapidly growing strains; whereas Mycophage V24 was sensitive to some rapidly growing strains only. Avian strains were resistant to both mycophages.

Construction and characterization of guaB-lacZ fusions in Escherichia coli K12.

GuaB-lacZ fusion strains of Escherichia coli K12 have been constructed using the Casadaban (1976) gene-fusion technique. The major modification to the procedure was the removal of the guanine requirement of Mu-induced guaA auxotrophs by introduction of a ColEl-gua+ plasmid prior to selection of the fusion. Conversion to prototrophy was necessary to overcome problems associated with repression of the gua operon by guanine added to selection media. Induction of the lysogenic fusion strains yielded plaque-forming lambda transducing phages that carried the lac genes and either the complete guaB gene and the gua promoter or only a distal portion of guaB.