Properties of Streptomyces phage SLE111

Streptavidin assay by means of biotinylated actinophages

Using D-biotinyl-N-hydroxysuccinimide ester, biotin was covalently attached to actinophage SLE 111. The chemically modified actinophage preparation (SLE 111-BIO) was prevented from forming plaques by biotin-binding proteins, such as streptavidin and avidin. The avidin concentration at 50% inactivation of biotinylated actinophages was 0.5 micrograms/ml. The streptavidin assay was useful as pre-selection method during the screening and improvement work with streptavidin-producing microorganisms.

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.