Studies on ATP-dependent deoxyribonuclease of Haemophilus influenzae: involvement of the enzyme in the transformation process

An ATP-dependent deoxyribonuclease deficient mutant of Haemophilus influenzae has been isolated on the basis of sensitivity to methyl methane sulfonate (mms). Furthermore, the involvement of the ATP-dependent deoxyribonuclease in the process of transformation in H. influenzae has been demonstrated. Among the 75 mms-sensitive mutants, two mutants lacking ATP-dependent deoxyribonuclease were isolated. One mutant $\text{Rd}\text{mms-s}$ 21 has no measurable ATP-dependent deoxyribonuclease activity, is almost transformation deficient and has normal DNA uptake after being submitted to competence protocole. The second ATP-dependent deoxyribonuclease deficient mutant which has abnormal DNA uptake is still under investigation. Furthermore, the enzyme deficient mutant mms-s 21 transformed back to mms-resistance, recovers the ATP-dependent deoxyribonuclease as well as the transforming ability. The involvement of the ATP-dependent deoxyribonuclease in the process of transformation in H. influenzae is therefore positively established.