Contribution to the Characterization of Bacillus megaterium

Abstract

A study of the cellular and colonial morphologies, the deoxyribonucleic acid (DNA) base composition, the degree of lysis by lysozyme, and some fundamental biochemical reactions was carried out on 23 strains previously identified as members of Bacillus megaterium. Included among these was NCTC 10342, the neotype strain of B. megaterium. The results showed that, primarily on the basis of their biochemical reactions, two of the strains belong to B. cereus, two belong to B. subtilis, and 19 belong to B. megaterium. The first two strains mentioned above clearly differed from B. megaterium strains with respect to their DNA base composition (33.2 and 34.3 mol% guanine plus cytosine [G+C]), their lysis by lysozyme (5.6 and 6.6%), and the morphology of their macro-and microcolonies. These properties were not helpful in differentiating the other two strains from the B. megaterium strains, for the two strains showed high G+C values (45.9 and 47.4 mol%) and high values of lysis by lysozyme, (92.9 and 96.7%). The 19 remaining strains, confirmed as members of B. megaterium, had G+C contents which varied from 37.3 to 43.0 mol% and lysis percentages which varied from 67.0 to 94.9. For these strains, a significant (P < 0.05) correlation was found between the DNA base composition and lysis by lysozyme. Three biogroups were established on the basis of the biochemical reactions of the 19 strains. These biogroups are similar to the “aggregate” and the “intermediate” strains of B. megaterium established by Gordon et al.