Effect of Sporulation Conditions on Chemical Composition and Biological Properties of Bacillus Megaterium Spores

Abstract

1. A chemically defined medium for Bacillus megaterium has been developed. Relationships have been obtained between the concentrations of each of the essential nutrients and final culture population. This enables the medium to be manipulated such that any desired component is present at a growth limiting concentration and all other components are present in controlled excess. 2. Spores were produced when the medium became depleted of glucose, ammonium, sulphate or phosphate, but were not produced when manganese, potassiwn or magnesium limited the vegetative growth of the culture, Spores were formed when a culture became simultaneously depleted of magnesium and glucose. 3. Spore suspensions were produced from complex media, and from defined media containing different concentrations of added manganese in which, a) glucose alone was growth limiting (G-), and b) glucose and magnesium were simultaneously depleted (G- Mg-). 4. Spores from G- Mg- media were significantly larger than those from G- media. Spores from agar were of intermediate volume. 5. The dipicolinic acid (D.P.A.), calcium and magnesium concentrations were in the ranges commonly quotedfor bacterial spores, and were generally unrelated to medium composition. 6. The heat resistance of the various spore varieties depended upon medium composition, but bore no consistent relationship to the D.P.A. and cation contents. Spores from G- Mg- media with high manganese content characteristically exhibited a shoulder on a thermal inactivation plot, those from all other media exhibited a log-linear survivor curve. 7. The rates of release of D.P.A. and cations from different spore suspensions appeared to be related to their heat resistance. 8. Spores from G- media exhibited more rapid and extensive germination (without prior heat activation) in a phosphate buffered solution of glucose and L-alanine than did spores from G- Mg- media. The initial rate of germination was aauced in spores from media with high manganese content.