FURTHER BIOLOGICAL AND MOLECULAR CHARACTERIZATION OF ACTINOPHAGE VWB

The development cycle of the temperate actinophage VWB was investigated. Adsorption of most phage particles occurred within 30 min and the adsorption constant was 0.6 x 10-8 ml min-1. The latent and rise periods were 140 and 100 min, respectively, and the burst size was estimated to be 130-250 p.f.u. Although phage VWB could infect only Streptomyces venezuelae ETH 14630 (ATCC 40755), of six different S. venezuelae strains tested, phage DNA could be introduced by transfection into most non-infectible strains. Upon transfection, phage DNA was propagated in these non-infectible strains and phage particles were released. In addition, the transfected strains could be lysogenized. By comparison of restriction fragments of VWB DNA, either free or integrated in the chromosomal DNA of the S. venezuelae ETH 14630 lysogen, the attachment site was localized. PAGE of the phage proteins revealed at least 17 different proteins with three major bands estimated as 16.5, 27.2 and 43 kDa in size. The N-terminal amino acid sequence of these supposed major head and tail proteins was determined. The corresponding DNA sequences on the phage genome were localized using oligonucleotides synthesized on the basis of the N-terminal amino acid sequences. The genes coding for the major structural proteins were shown to be clustered, as has been observed for other bacteriophages.