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A total of 17 of 21 Lactobacillus strains of the subgenus Streptobacterium were lysogenic. Two different temperate phages isolated from such lysogens are very similar to Lactobacillus casei phage PL-1. The narrow host range of bacteriophage PL-1 appears to be caused by homoimmunity.
Cleavage maps of the three similar Bacillus subtilis temperate bacteriophages, phi105, rho10, and rho14, were constructed by partial digestion analysis utilizing the restriction endonuclease EcoRI. Comparison of the topography of these maps indicates that all phage DNAs posses cohesive ends and a number of EcoRI restriction sites; the fragments are conserved, and the estimated base substitution/nucleotide divergence between these phages is 0.03 to 0.07 based on conserved fragments or between 0.03 and 0.11 based on conserved cleavage sites. These lines of evidence indicate that phi105, rho10, and rho14 are closely related. Double-enzyme digestion analysis reveals that rho14 DNA has unique SalGI and BglII restriction sites and phi105 DNA has a unique SalGI restriction site, making these phages possible cloning vectors for B. subtilis.
Bacteriophage phi105 is a temperate bacteriophage for Bacillus subtilis 168. Temperature-sensitive and plaque mutants of phi105 were isolated. The results of two- and three-factor crosses with these mutants suggest the vegetative map of phi105 to be circular. The location of prophage phi105 between bacterial markers phe-1 and ilvA1 was shown by means of PBS1 transduction. Five markers in the prophage were linearly ordered with respect to the bacterial markers. Linkage between bacterial and prophage markers was demonstrated in transformation experiments with deoxyribonucleic acid extracted from lysogenic bacteria. The data demonstrate that prophage phi105 is linearly inserted into the bacterial chromosome.
Bacteriophage phi105 is a temperate phage for the transformable Bacillus subtilis 168. The infectivity of deoxyribonucleic acid (DNA) extracted from mature phi105 phage particles, from bacteria lysogenic for phi105 (prophage DNA), and from induced lysogenic bacteria (vegetative DNA) was examined in the B. subtilis transformation system. About one infectious center was formed per 10(8) mature DNA molecules added to competent cells, but single markers could be rescued from mature DNA by a superinfecting phage at a 10(3)- to 10(4)-fold higher frequency. Single markers in mature DNA were inactivated at an exponential rate after uptake by a competent cell. Prophage and vegetative DNA gave about one infectious center per 10(3) molecules added to competent cells. Infectious prophage DNA entered competent cells as a single molecule; it gave a majority of lytic responses. Single markers in sheared prophage DNA were inactivated at the same rate as markers in mature DNA. Prophage DNA was dependent on the bacterial rec-1 function for its infectivity, whereas vegetative DNA was not. The mechanism of transfection of B. subtilis with viral DNA is discussed, and a model for transfection with phi105 DNA is proposed.
Temperate Bacillus phage phi105 is serologically unrelated to previously described virulent Bacillus phages. Phage phi105 is incapable of generalized transduction. Prophage phi105 is inducible with mitomycin C. Phage phi105 contains double-stranded deoxyribonucleic acid (DNA) with a molecular weight of about 25 x 10(7) as determined by band sedimentation and electron microscopy. The per cent guanine plus cytosine of phi105 DNA is 43.5 as determined by buoyant density in CsCl and by thermal denaturation. Phage phi105 DNA may contain complementary single-stranded ends.
A new temperate bacteriophage (phage Psi) of Agrobacterium tumefaciens strain B91 is described. Many octopine-utilizing strains of A. tumefaciens harbor prophage Psi or a phage that is similar if not identical to it. This phage has a very narrow host range, and we found that its growth is strongly reduced in strains which carry an octopine pTi plasmid. When sensitive bacteria are infected with Psi, 1 to 3% of the survivors carry mutations on the chromosome, as well as on the pTi plasmid. This phenomenon appears to be a direct consequence of lysogenization. The possible mechanisms whereby such Psi-induced mutations occur are discussed.
The temperate phage 59 from Erwinia carotovora and its DNA were studied. The phage particles have an icosahedral head and a long noncontractile tail with a base plate. The virus DNA makes up 50% of the total virus and exists as a linear molecule (molecular weight, 2.6 X 10(7)). A model of virus structural organization is presented.
Radiolabeled phage SPO2 fragments were tested for the abiity to form interspecies deoxyribonucleic acid (DNA) duplexes with DNA from Bacillus subtilis and from phages beta3 and beta22. No reassociation, above control values, occurred between the DNA of phage SPO2 and that of its host or either of the virulent B. subtilis phages. It appears that extensive nucleotide sequence similarities between portions of host and phage DNA species are not necessary for the formation of the lysogenic state. The thermal elution profile of reassociated SPO2 DNA exhibited a normal distribution, indicating no heterogeneity in base composition. This differs from temperate enterophages whose DNA molecules contain regions of differing base composition.
Temperate Bacillus subtilis phage SPO2 codes for a phage-specific DNA polymerase. The polymerase gene has been cloned, and its nucleotide sequence has been determined. Within the sequence there is an open reading frame starting with a TTG and ending with three consecutive translational stop codons. Ten base pairs upstream from the proposed TTG initiation codon there is a probable ribosome-binding site with a calculated free energy of interaction with the 3' end of B. subtilis 16S rRNA of -15 kcal (-63 kJ)/mol. Based on the sequence and the expression of the polymerase gene in three different hybrid plasmids, we conclude that this open reading frame is the structural gene for SPO2 DNA polymerase. The predicted molecular weight of the polymerase is 72,486. In hybrid plasmid pJB74, the terminal triplet of an open reading frame with coding capacity for a protein of ca. 10 kilodaltons overlaps with the translational initiation triplet TTG of the polymerase gene. We speculate that transcription and translation of this open reading frame can influence the amount of phage DNA polymerase made in SPO2-infected bacteria.
The cohesive single-stranded ends of temperate Bacillus subtilis phage phi 105 were analyzed with the exonuclease activities of the Klenow fragment of DNA polymerase I and with exonuclease III and were found to be 3' extensions. Chemical sequencing of 3'-end-labeled fragments showed that the ends are 7-base extended 3' single strands and have the sequence: 5'-GCGCTCC-3'. 3'-CGCGAGG-5'
Temperate coliphage HK253 integrates near the proAB locus on the Escherichia coli K-12 chromosome. It can bring about specialized transduction of proAB and phoE mutants of E. coli, but it is incapable of general transduction. One of the proline-transducing particles was found to be nondefective.
We have characterized three temperate bacteriophages of pneumococcus (HB-3, HB-623, and HB-746). Although all the phages belong to the same family, the polypeptide composition of the virions and the DNA restriction endonuclease analysis of their DNAs revealed differences among the three phages. The genomes of these bacteriophages have been isolated as DNA-protein complexes. The protein is specifically associated with the two 5' termini of the DNA as shown by experiments carried out with exonucleases. The protein bound to the DNA in the three phages studied, iodinated in vitro with 125I, has a molecular weight of 23,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Treatment of the complexes with chaotropic agents suggested that the protein is covalently bound to the 5' termini of the DNA. Comparative pulsed-field gel electrophoresis analysis and Southern hybridization of the SmaI restriction fragments of DNAs from one lysogenic bacteria and its parental strain revealed that the prophage genome was integrated in the host chromosome.
Combined Southern blot hybridization analyses of DNA digests of several clinical strains of Streptococcus pneumoniae have revealed the presence of a gene (hblR), or part of it, similar to the hbl7 gene coding for the cell wall lytic enzyme of the temperate HB-746 phage. The results confirmed that the genome of HB-746, which contains protein covalently linked to the 5' ends of its DNA, becomes integrated into the host strain 8R1 and showed that both the host and phage attachment sites, attB and attP, lie downstream of the 3' end of the structural region of the hblR and hbl7 genes, respectively. The data reported also highlight some evolutionary relationships between phage and bacteria.
We have characterized a temperate phage (MM1) from a clinical isolate of the multiply antibiotic-resistant Spanish/American 23F Streptococcus pneumoniae clone (Spain(23F)-1 strain). The 40-kb double-stranded genome of MM1 has been isolated as a DNA-protein complex. The use of MM1 DNA as a probe revealed that the phage genome is integrated in the host chromosome. The host and phage attachment sites, attB and attP, respectively, have been determined. Nucleotide sequencing of the attachment sites identified a 15-bp core site (5'-TTATAATTCATCCGC-3') that has not been found in any bacterial genome described so far. Sequence information revealed the presence of an integrase gene (int), which represents the first identification of an integrase in the pneumococcal system. A 1.5-kb DNA fragment embracing attP and the int gene contained all of the genetic information needed for stable integration of a nonreplicative plasmid into the attB site of a pneumococcal strain. This vector will facilitate the introduction of foreign genes into the pneumococcal chromosome. Interestingly, DNAs highly similar to that of MM1 have been detected in several clinical pneumococcal isolates of different capsular types, suggesting a widespread distribution of these phages in relevant pathogenic strains.
Actinophage phiC31 isolated from Streptomyces coelicolor A3(2), the only strain among actinomycetes for which a genetic map had been constructed, appears to be a typical temperate phage. After phiC31 infection, true lysogenic cultures arose which liberated phage and were immune to infection with homologous phage after repeated single-colony isolations and treatment with phage-specific antiserum. Clear-plaque (c) mutants were derived from phiC31 phage which failed to lysogenize sensitive cultures. Actinophage phiC31 has a temperature-sensitive stage of reproduction. A phage which reproduces with the same effectiveness at high (37 C) and low (28 C) temperatures has also been obtained. Heat-inducible (ct) mutants were isolated from this phage which were able to lysogenize sensitive cultures at 28 C but failed to do so at 37 C. Properties of ct mutants suggest that ct mutations involve a gene controlling maintenance of the lysogenic state in actinomycetes and synthesizing repressor, which may become heat-sensitive as a result of mutation.
SPO2 and phi105 are temperate Bacillus subtilis bacteriophages which have been suggested to belong to a cluster of related bacteriophages. In the present work, we show that SPO2 does not complement any of the 11 essential genes known in phi105 and that the phages do not recombine. Deoxyribonucleic acid (DNA)-DNA hybridization shows less than 10% homology between SPO2 and phi105 DNA. DNA synthesis in phi105 shows a greater dependence on host functions than does SPO2 DNA synthesis. Growth of phi105 but not of SPO2 is inhibited by the uracil analogue 6-(p-hydroxyphenylazo)-uracil. Infection of a DNA polymerase-deficient strain of B. subtilis with SPO2 leads to an increase in DNA polymerase activity in crude extracts, whereas no such increase is found after infection of this strain with phi105. It is concluded that SPO2 and phi105 are unrelated bacteriophages.
Bacteria belonging to the genera Rhizobium, Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Azorhizobium (collectively referred to as rhizobia) grow in the soil as free-living organisms but can also live as nitrogen-fixing symbionts inside root nodule cells of legume plants. The interactions between several rhizobial species and their host plants have become models for this type of nitrogen-fixing symbiosis. Temperate legumes such as alfalfa, pea, and vetch form indeterminate nodules that arise from root inner and middle cortical cells and grow out from the root via a persistent meristem. During the formation of functional indeterminate nodules, symbiotic bacteria must gain access to the interior of the host root. To get from the outside to the inside, rhizobia grow and divide in tubules called infection threads, which are composite structures derived from the two symbiotic partners. This review focuses on symbiotic infection and invasion during the formation of indeterminate nodules. It summarizes root hair growth, how root hair growth is influenced by rhizobial signaling molecules, infection of root hairs, infection thread extension down root hairs, infection thread growth into root tissue, and the plant and bacterial contributions necessary for infection thread formation and growth. The review also summarizes recent advances concerning the growth dynamics of rhizobial populations in infection threads.
The 20 patients described could be included in the group of patients diagnosed as ;idiopathic steatorrhoea'. However, their histories were short and diarrhoea was not a major feature. Since megaloblastic anaemia due to folic acid deficiency was a common feature it is suggested that these patients may form a homogeneous group and the diagnostic label of temperate sprue is suggested.