Bacteriophages ofClostridium saccharoperbutylacetonicum

Abstract

The action of DNase on HM 2 phage during DNA penetration was studied. Clostridium saccharoperbutylacetonicum, a host of HM phages was incubated in long-heated (L.H.) TYA broth at 30°C, transferred to restricted nutrition (R.N.) broth, and incubated at 30°G for certain periods. HM 2 phage (group 1) was added to the incubation mixture at an appropriate multiplicity of infection. This cell-phage mixture was treated with DNase (10 to 40 μg per ml) for 7 min at 30°C. When DNase was added within 4 min after the addition of the phages, the infection of HM 2 phages was inhibited 25 to 35 per cent. DNase addition at later time had no effect. Free phages were never inactivated under these conditions. The uninfected host cells during DNase treatment retained the ability to form colonies. This inhibition was not due to the prevention of phage adsorption to host cells, but of phage DNA penetration. The optimal conditions for DNase inhibition on phage infection were as follows: (1) growth of host cells in L.H. Broth (first culture) for 10 to 12 hr, (2) 5 to 10 per cent inoculum of the first culture to a fresh R.N. broth, (3) growth of host cells in R.N. broth (second culture) for 2 to 4 hr and (4) 0.1 to 1.0 of the multiplicity of infection. The inhibition of HM 2 phage infection by DNase treatment was independent on the number of host cells and the environments in the reaction mixture, but dependent on the growth and physiological states of the host cells. These phenomena were not observed with HM 3 phage (group II).