Binding of transforming DNA to protoplasts isolated from competent Bacillus subtilis

Transforming 3H-labelled DNA binds specifically to protoplasts isolated from competent cultures of Bacillus subtilis. The bound DNA is fully accessible to added DNase I, indicating that protoplasts bind, but do not process donor DNA. A bi-phasic pattern of competition for binding with increasing amounts of unlabelled and labelled DNA was found. In these conditions, two levels of saturation appeared which correspond to two kinds of DNA receptor sites. Homologous DNA binds preferentially to the first kind of receptor (specific) and only at higher concentrations would bind to the second (unspecific) binding sites. Bound DNA forms a rather stable complex with some constituent(s) of the protoplasts.