Properties of a lytic enzyme produced by a strain of Bacillus subtilis

Cell multiplication studied with an electronic particle counter

Toennies, G. (Institute for Cancer Research, Philadelphia, Pa.), L. Iszard, N. B. Rogers, and G. D. Shockman. Cell multiplication studied with an electronic particle counter. J. Bacteriol. 82:857-866. 1961.-Suitable conditions are described for the application of the Counter electronic particle counter to the study of bacterial number and particle size distribution in growing cultures. When Streptococcus faecalis and Escherichia coli were each grown in a different medium, exponential growth was accompanied by a continuous decrease in average particle size. The average apparent particle volume of S. faecalis decreased by about 50% in five generations. Microscopic studies of S. faecalis indicated that this was due to a decrease in the average chain length of the cultures. The following observations concerning average particle size during exponential growth of S. faecalis in a synthetic medium were made: (i) A decreased concentration of tryptophan, serine, or proline resulted in a significant decrease in average particle size. Similar changes in numerous other nutrients produced no or only minor changes. (ii) The addition of a cytoplasmic extract prepared from exponentially growing cells resulted in changes similar to those resulting from the partial withdrawal from the medium of certain nutrients. (iii) The effect of the cytoplasmic extract could be counteracted by the addition of tryptophan. (iv) A limited survey, including the effects of the rate of exponential growth, mechanical agitation, the presence of indoleacetic acid, indole, kinetin, lysozyme, or ascorbate, disclosed no additional factor which significantly influenced the particle size distribution.

Visualization of endo-beta-N-acetylglucosaminidase, lysozyme, and lysostaphin after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate

Bacteriolytic enzymes of different bond specificities, denatured by sodium dodecyl sulphate (SDS), were electrophoresed in polyacrylamide gels containing bacterial cells, then renatured after removal of SDS by diffusion. Enzyme activity was seen in sharp transparent bands resulting from bacteriolysis in the gels, while these sections containing bacterial cells appeared cloudy. Bacteriolytic enzymes including staphylococcal endo-beta-N-acetylglucosaminidase, lysozyme (N-acetylmuramidase), and lysostaphin (endopeptidase) were detected. The major bacteriolytic enzymes of Staphylococcus spp. were identified in gels after electrophoresis of crude enzyme preparations. This demonstrates the wide applicability of this method to the study of staphylococcal bacteriolytic enzymes. However, it should be noted that the method will fail to detect activities of bacteriolytic enzymes which are irreversibly inhibited by SDS.

The functions of autolysins in the growth and division of Bacillus subtilis

Some bacteria, such as streptococci, exhibit growth from discrete and well-defined zones. In Streptococcus faecalis, growth zones can be observed in the electron microscope, and the position of the zone can be used as a marker for cell cycle events. Growth of the cell surface of Bacillus subtilis appears to be by a much different mechanism from that of streptococci. Cell elongation takes place by the insertion at many sites in the cell cylinder of peptidoglycan components. The insertion occurs on the inner face of the wall, and upon cross linking, the new wall material becomes stress bearing and older wall is pushed to the surface. When old wall reaches the surface, it becomes susceptible to excision by autolysins, resulting in wall turnover; cell elongation, due to the stretching of the cross-linked peptidoglycan, therefore, accompanies turnover and does not require a specialized growth zone.

Micrococcus lysodeikticus bacterial walls as a substrate specific for the autolytic glycosidase of Bacillus subtilis

The Bacillus subtilis 168 autolytic glycosidase degrades Micrococcus lysodeikticus cells or cell walls, whereas the B. subtilis autolytic amidase does not. The criteria used to establish this fact included: the determination of chemical bonds broken, heat-inactivated kinetics, pH dependence curves, and the physical separation of glycosidase from amidase. The physical separation involved LiCl elution from two different ion-exchange materials, walls from B. subtilis 168 strain betaAO, and walls from mutant strain betaA173 derived from strain betaAO. No evidence was obtained for B. subtilis vegetative bacteria making any more autolysins than one autolytic amidase and one autolytic glycosidase.