Inhibitory Effect of Protamine on the Growth from the Spores of Two Bacillus Species

Abstract

Inhibitory effect of clupeine and salmine sulfates on the growth from the spores of Bacillus sub-tilis and Bacillus licheniformis was investigated. These two protamines were found effective in pre-venting the growth from the spores in both agar and broth media. The level of protamine required to inhibit the growth was found to be more or less dependent on the type of media used and the pH. In general MIC of the protamines ranged from 100 to 150μg/ml in nutrient agar and 10 to 50μg/ml in broth but higher protamine level was required in nutritionally rich Heart Infusion Broth and Penassy Broth. Inhibitory effect of protamine was more profound in the neutral and alkaline pH than in the acidic condition. Filter sterilized and autoclave sterilized protamine had the same inhibitory effect. Spore density in the medium influenced the required level of protamine for preventing the growth from the spores.