Effect of some lytic agents on Aerobacter aerogenes.

Abstract

IN the course of a study of the surface structures of Aerobacter aerogenes the action of lysozyme has been investigated. Preliminary experiments indicated that the enzyme produced no observable changes in the optical density of cell suspensions. In an attempt to promote enzymic attack the conditions were varied by altering the concentration of lysozyme, the time and temperature of incubation, the origin and age of the bacteria, and the pH of the suspensions. Cells were also incubated with lysozyme and various concentrations of sodium chloride, magnesium chloride, versene1 and tris-buffer2. No lysis which could be attributed to the action of lysozyme was observed under any of these conditions. Microscopic studies showed the appearance, in solutions containing 20 per cent sucrose, of spherical bodies, which were probably similar to the protoplasts obtained by Weibull3 from B. megatherium. These, however, did not constitute more than 1 per cent of the cell population, except in one case, when bacteria incubated overnight with a 2 per cent solution of lipase were subjected to the action of lysozyme in 20 per cent sucrose. About 5 per cent conversion to spheres was observed. In a test for the presence of lysozyme substrate in the cell walls of Aerobacter aerogenes, washed cells were suspended in saline at pH 3.6 and incubated for 1 hr. at 40° C. with 200 µgm./ml. of lysozyme4. The optical densities of the suspensions were measured before and after incubation. The pH was adjusted to 10.0 by the addition of sodium hydroxide and the optical density measured immediately. A comparison with the results of a similar experiment in the absence of the enzyme showed that there was some lysis due to lysozyme. The specific substrate is thus present in the cell walls of the organism, but it is doubtful whether the amount available to the enzyme is sufficient to permit extensive lysis.