Competitive inhibition of transformation in group H Streptococcus strain Challis by heterologous deoxyribonucleic acid.

Glucosylated deoxyribonucleic acid (DNA) from phages T4 and T6 competes poorly with homologous DNA causing only a slight decrease of transformation in Group H Streptococcus strain Challis. Other types of heterologous DNAs (Micrococcus luteus, Clostridium perfringens, Escherichia coli, calf thymus and non-glucosylated phage T6 DNA), in contrast to glucosylated T4 and T6 DNAs, compete with transforming DNA to the normal, high extent. These results indicate that as in transformation of Bacillus subtilis, the presence of glucose attached to 5-hydroxymethylcytosine in phage T6 DNA considerably decreases the interaction of such DNA with competent cells of the Challis strain. It also indicates that the guanine plus cytosine content of DNA is not decisive in determining its interaction with competent cells.