PROTEOLYTIC ACTIVITY OF BACILLUS SUBTILIS IN A CLAY–PROTEIN PASTE SYSTEM ANALOGOUS TO SOIL

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Abstract
The proteolytic specificity of a purified proteinase, Nagarse, of Bacillus subtilis N′ towards denatured lysozyme was compared with that of the organism growing in a model soil system consisting of a heat-denatured lysozyme–kaolinite complex in a paste form which represents the natural habitat of soil organisms. The use of a sterile technique and a specially designed apparatus permitted periodic withdrawal of nonadsorbed and nonassimilated proteolysis products from the medium; such products were formed by the proteolytic activity of exoenzymes excreted by B. subtilis N′. A chromatographic comparison was made between the proteolysis products of B. subtilis N′ growing in the lysozyme–kaolinite system and those of the proteinase Nagarse acting on denatured lysozyme in solution; some differences were observed. The growth rate studies indicated that the lag period of growth of B. subtilis N′ in the lysozyme–kaolinite complex extended up to one day. The bacteria excreted exoenzymes during this lag period, which hydrolyzed the substrate protein, but the proteolysis products were not assimilated until the exponential growth period started.