Correlation between the occurrence of competence in the transformation of group HStreptococci and the presence of the competence factor and thein vitro DNA-inactivating factor

Summary

In experiments with strains of group H streptococci (S. challis, S. wicky, S. blackburn, S. channon, andS. wicky transformants producing the competence factor) new observations were made suggesting that the occurrence of competence is associated not only with the presence of the competence factor (cpf) but also with thein vitro DNA-inactivating group H streptococcal factor (iF) which was previously described by us.

The iF preparations—cell surface extracts—were shown to contain nuclease, most likely DNase. The iF activity increased after short heating at 90°. Further evidence was presented that cpf and iF are separate activities. The non-transformable strainsS. blackburn and S.channon were found to produce cpf.

Proteolytic enzymes, when added to the culture several minutes prior to, or at the competence peak, were found to increase markedly the transformation yield, at the same time making it impossible to detect cpf in the cell extracts. This observation may suggest that the presence of cpf in cell layers accessible to the enzymes is not necessary in the period when DNA is taken up, although cpf has to be produced previously by the recipient or has to be in contact with it. Enzyme addition did not influence the iF activityin vivo.

In crude iF preparations a factor was detected which inactivates cpfin vitro.

Some aspects of the competence mechanism are discussed.