Susceptibility of Several Microorganisms to Milk Lysozymes,

Abstract

Several Gram-positive and Gram-negative bacteria were found to be susceptible to different degrees to purified bovine milk and human milk lysozymes. Sodium chloride accelerated the lysis of both live and ultraviolet-killed cells of Micrococcus lysodeiktieus and Sarcina lutea by the two milk lysozomes. However, the lysis of other bacteria sensitive to the lysozymes was impaired by sodium chloride. In general, ethylenediaminetetraacetate augmented the lysis of both live and ultraviolet-killed cells of Bacillus subtilis by bovine milk lysozyme and that of Pseudomonas acruginosa by both bovine and human milk lysozymes. However, the lysis of other sensitive bacteria, under the same conditions of assay, was depressed by ethylenediaminetetraacetate. In the case of live, actively growing bacteria, the additions of either sodium chloride or ethylenediaminetetraacetate, in general, improved the lysis of the sensitive organisms by the milk lysozomes and egg-white lysozome. For the lysis of Escherichia coli and Bacillus cereus, sodium chloride and ethylenediaminetetraacetate, respectively, were found to be essential. The study indicated that milk lysozomes may play a significant role in the inherent anti-bacterial activity of milk. © 1969, American Dairy Science Association. All rights reserved.