Biotransformation of cholesterol by Micrococcus species mediated by plasmid DNA

A steroid-biotransforming strain RJ6 was identified as Micrococcus roseus. This bacterium has a 10 kb plasmid pMQV10. Curing mediated through cultivat ion of the culture with a low concentration (200 ng/ml) of mitomycin C is d escribed. Loss of cholesterol degradation (chol(+)) and streptomycin resist ance (Sm-r) phenotypes as a consequence of the loss of plasmid indicate the extrachromosomal location of these two genes in this strain. An electropor ation procedure was developed for transformation of cured strain of Microco ccus (RJC6) by plasmids. Frequency of greater than 10(5) transformants/mu g DNA was achieved, which is 100-fold higher than the standard transformatio n procedure that yielded 5.3x10(3) transformants/mu g DNA in the same strai n.