Characterization of the virulent actinophage S2

Inverted repeats in the DNA of Streptomyces plasmids pMG110 and pMG120

Two cryptic plasmids pMG110 (10.5 kb) and pMG120 (14.5 kb) isolated from Streptomyces luteolutescens were cleaved by restriction endonucleases Bg/II, KpnI, and SalGI. A physical map was constructed for pMG110. After denaturation and intrastrand reannealing, two types of snap-back structures were identified by electron microscopy, differing in the size of the loop (type 1, 1 kb; type 2, 1.6 kb), whereas the stem of both structures was about 190 bp long. Stem-loop structures of similar size were also observed in pMG120. In rare cases, both types of elements were present on the same DNA molecule. The analysis of Bg/II- and KpnI-generated fragments allowed the localization of the elements at two alternative positions on the physical map of pMG110.

Gene expression after transformation of Streptomyces lividans protoplasts with plasmid pIJ2 DNA

A new method has been developed for the selection of antibiotic-resistant clones after transformation of Streptomyces protoplasts with plasmid DNA. This method is based on establishing a spatial concentration gradient for the antibiotic, the resistance to which is encoded by the transforming plasmid. By this method, the resistance development of regenerating protoplasts can be followed. The results suggest that antibiotic resistance is inducible. In addition, we were able to show that resident plasmids incompatible with the incoming ones are eliminated when this direct selection principle is used. Moreover, this method, which may facilitate the application of gene technology in Streptomyces, works even though the transformation procedure gives variable results.

Transduction in Streptomyces hygroscopicus mediated by the temperate bacteriophage SH10

The temperate actinophage SH10 mediates generalized transduction in Streptomyces hygroscopicus at low frequency. The efficiency of transduction depends on the average phage input, age of outgrowing spores of the recipient and on the selective marker. The highest EOT was found for the auxotrophic mutants 21(phe-) and 5(try-) (4.2 x 10(-6) and 2.7 x 10(-6), respectively). Transduction of the thermosensitive mutant NG14-216 ts 35 was two orders of magnitude lower (2.5 x 10(-8)). The transductant colonies segregated into stable and unstable clones. Stable transductants were never found to be lysogenic for phage SH10.

Interaction of bacteriophage O2 with strains of the genus Oerskovia

Bacteriophage O2 multiplies normally on Oerskovia turbata IMET 47 153. It has a burst size of about 100 p.f.u. per infected cell and a latent period of 100 min at 30 degrees C. On Oerskovia xanthineolytica IMET 47 383 clear spots were formed after addition of high phage concentrations onto agar top layers. By phase contrast observation, and measurement of the optical density of infected cultures, it was found that the clearing effect on strain IMET 47 383 was due to lysis-from-without. Phage O2 adsorbs and injects its DNA into cells of strain IMET 47 383 but phage multiplication does not occur, and the phage DNA becomes degraded. Inhibition of phage DNA injection by the combined action of xanthotoxin -- u.v. irradiation abolished the clearing activity of phage lysates. Therefore, both adsorption and DNA injection seem to be prerequisites for the release of a lytic activity out of the phage particle, which is responsible for the clearing effect on strain IMET 47 383.

Transfection of protoplasts from Streptomyces lividans 66 with actinophage SH10 DNA

The slightly modified procedure for the transformation of protoplasts of S. coelicolor A3 (2) with SCP2 plasmid DNA and polyethylenglycol (PEG) (Bibb et al., 1978) was extended to infection of protoplasts of S. lividans 66 with actinophage SH10 DNA (Klaus et al., 1979). Maximal yield of transfected protoplasts was obtained at 20% PEG, 3 MM sodium-citrate and 150 mM NaCl final concentrations. The efficiency of transfection was determined to be about 2 x 10(-8) to 2 x 10(-7). The average value of competent protoplasts was about 1-2 x 10(-4) of regenerating protoplasts. In comparison with outgrowing spores infected with phage particles the average burst size of transfected protoplasts was reduced from 100 to 10 pfu/infected cell, the latent period prolonged from 45 min to 120 min and the rise period was not affected.

Molecular characterization of the genomes of actinophages SH3, SH10, SH11, and SH12 infecting Streptomyces hygroscopicus

Some physico-chemical properties of the DNAs released from the actinophages SH3, SH10, SH11, and SH12 are described. The four phage DNAs have a linear double-stranded secondary structure and are unique with respect to their high G.C contents which, from melting studies and buoyant density experiments, were found to be in the range of 68-73 mol-%. The DNA molecular weights were determined by sedimentation velocity experiments and by electron microscopic length measurements, the mean values of the two corresponding data sets being 34.0 x 10(6) (SH3), 26.7 x 10(6) (SH10), 26.1 x 10(6) (SH11), and 28.7 x 10(6) (SH12) with a mean relative error of +/- 5%. From different observations it was concluded that SH10 DNA, and possibly also SH11 and SH12 DNA, have cohesive ends and can undergo intramolecular or intermolecular association to form ring-like monomers or linear and ring-like multimers. Cleavage of the DNAs of SH3, SH10, SH11, and SH12 by EcoRI restriction endonuclease delivered two, one, zero, and two cleavage sites, respectively, and by BamHI restriction endonuclease eight, zero, zero, and zero cleavage sites, respectively.