Non-flocculating mutants derived from deoxyribonuclease-susceptible floc forming Pseudomonas sp.

Nine mutant strains defective in flocculating abilities were derived from the flocculating parent Pseudomonas strain C-120. Mutations in flocculating ability did not influence the rate and extent of cell growth. Amongthem, six strains which did not form floes at all completely lacked DNAbinding activity. Other mutant strains formed floes to a lesser extent as compared with the parent. Cell envelopes and SDS-extracted envelopes prepared from the parent strain, but not from nonflocculating mutant strains, held DNA-binding activities, indicating that DNA-binding activities of cell envelopes and SDS-extracted envelopes represented that of the wild type cells responsible for flocculation. DNA-binding activities of cell envelopes were abolished by treating with proteases, suggesting that the DNAbinding factor is a proteinaceous component. Susceptibility of DNAbinding activities of SDS-extracted envelopes to 2, 4, 6-trinitrobenzene sulfonic acid or at high temperatures supported this assumption. Although cell envelopes prepared from the parent cells and mutant cells were subjected to SDS-polyacrylamide gel electrophoresis, no differences in protein composition were observed.