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pubmed:abstractText |
The distribution of alkaline phosphatase and nuclease activity between cells and medium was examined in one strain of Bacillus licheniformis and four strains of B. subtilis. Over 95% of both activities was found in the medium of the B. licheniformis culture, but in the B. subtilis cultures the amount of enzyme activity found in the medium varied with the strain and the enzyme considered. B. licheniformis 749 and its penicillinase magnoconstitutive mutant 749/C were grown in continuous culture with phosphorous as the growth-limiting factor, and the kinetics of penicillinase formation and secretion were examined. Nutrient arrest halted secretion (usually after a lag of about 30 min) in both the inducible and constitutive strains. Chloramphenicol did not eliminate secretion, but under certain circumstances reduced its rate. In the inducible strain treated with a low level of inducer, the rate of secretion was more affected by the rate of synthesis than by the level of cell-bound enzyme. During induction, the onset of accretion of cell-bound penicillinase and secretion of the exoenzyme were nearly simultaneous. It seems unlikely that a long-lived, membrane- or cell-bound intermediate is mandatory in the secretion of the three enzymes by Bacillus species. In the case of penicillinase secretion, there are at least two different phases. When penicillinase synthesis is proceeding rapidly, the rate of secretion is five to six times greater at equivalent concentrations of membrane-bound penicillinase than it is when penicillinase synthesis is reduced. The data require that any membrane-bound intermediate in the formation of exoenzyme be much shorter-lived in cells with a high rate of synthesis than in cells with a low rate. Either there are two separate routes for the secretion of penicillinase or the characteristics of the process vary substantially between the early stages and the declining phase of induction.
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