Isolation of viable deletion mutants of Streptomyces actinophage (Pal 6) and their molecular characterization

Structural characteristics of the Corynebacterium lilium bacteriophage CL31

Bacteriophage CL31 was isolated on a Corynebacterium lilium strain. Out of 30 strains tested, only CL31 was able to form plaques on Corynebacterium glutamicum ATCC 13287, Brevibacterium lactofermentum ATCC 21086, and Arthrobacter sp. strain SI55, but at a very low frequency. This phage belongs to group B of Bradley's classification (D. E. Bradley, Bacteriol. Rev. 31:230-314; 1967). Its head is 53 nm in diameter, and its tail is 396 nm in length. The phage capsid contains three major proteins, of 12.5, 29.0, and 37.0 kilodaltons, and five minor ones (23.9, 26.0, 27.0, 40.0, and 55.4 kilodaltons). CL31 DNA is a linear molecule of 48 kilobases with cohesive ends. Restriction mapping was performed for endonucleases BglII, EcoRI, SalI, and KpnI. The expression of CL31 genes in Escherichia coli was studied by the maxicell technique; 12 different proteins were detected.

Characterization of bacteriophages infecting Streptomyces erythreus and properties of phage-resistant mutants

Three bacteriophages infecting Streptomyces erythreus, called G3, G4 and G5, were isolated and characterized. They contain double-stranded linear DNA molecules with cohesive ends. The restriction map of G3 DNA (48 kilobases long) for four restriction endonucleases and that of G4 DNA (43 kilobases long) for seven restriction endonucleases are reported. Restriction analysis and hybridization experiments showed that G3 and G4 share little DNA homology, while G4 and G5 are apparently identical except for an additional EcoRI site present in G5. The region containing this EcoRI site has been mapped on G4 DNA. Microbiological and serological data showed that G5 is very similar to G4. G3- and G4-resistant mutants of S. erythreus PS1 were isolated. The screening of phage-resistant mutants showed a high frequency of strains with increased erythromycin production. The mechanism of phage resistance of strain PS3 (G3 resistant) and of strain PS16 (G4 resistant) was examined. The DNA of the resistant strains contains no phage DNA, ruling out lysogeny as a cause of phage resistance. Transfection of strains PS1, PS3, and PS16 with DNA of the three phages showed the same efficiency, indicating that resistance is at the level of the bacterial wall.

A restriction endonuclease map of Streptomyces phage VWB

A physical map of the actinophage VWB has been constructed using the restriction endonucleases BglII, ClaI, EcoRI, EcoRV, HindIII, KpnI and SphI. Phage VWB, genome size 47.3 kb, propagates on Streptomyces venezuelae, and it can also lysogenise this species. The three BglII-generated fragments of VWB DNA were cloned in pBR322, and subsequently mapped. In this manner the restriction map of the VWB phage genome was constructed.

Isolation and characterization of the Streptomyces cattleya temperate phage TG1

A temperate actinophage, TG1, was isolated from soil by growth on Streptomyces cattleya and has been shown to be potentially useful for the cloning of DNA in this organism and other streptomycetes. It forms stable lysogens by integration at a unique site on the chromosome. The phage genome consists of 41 kb of double-stranded DNA with cohesive ends. It has unique sites for ClaI, NdeI, PstI, SmaI, and XbaI. The PstI site has been shown to be in a dispensable region of the phage genome. Deletions (2 kb in length) were obtained which retain this site and should be useful for the cloning of DNA.

Restriction enzyme mapping of the DNA of Streptomyces bacteriophage B alpha and its deletion derivatives

Cleavage analysis of actinophage B alpha DNA was done with several restriction enzymes, and a restriction map of the DNA was determined. The DNA appeared to carry cohesive ends. Deletion mutants of actinophage B alpha were isolated by five cycles of treatment with 15 mM PPi. Both mutants had deletions of 2.5 of 1.8 megadaltons near one end of the genome, and one of them lost the single EcoRI cleavage site.