Sporulation in Bacillus subtilis. Properties and time of synthesis of alkali-soluble protein of the spore coat

Abstract

An alkali-extractable protein fraction comprising 6% of the dry weight of the spore can be removed from spores of Bacillus subtilis 168. Three different extraction procedures each yield at least one similar protein. Extracted protein behaved as a single species on ion-exchange chromatography or gel filtration, but two polypeptides were found on electrophoresis. Comparison of molecular weights on electrophoresis and by sucrosegradient analysis suggests that the protein(s) undergo aggregation into multimers. Extracted spores remain viable, but are altered in density and lysozyme sensitivity and they aggregate together. Electron microscopy of extracted spores shows that loss of material seems to occur from the outer coat layers. Extraction therefore probably removes a specific fraction of the spore-coat protein, but without impairment to the spore protoplast. This protein can first be detected immunologically 4h after the initiation of sporulation, and the synthesis of this protein is sensitive to chloramphenicol, actinomycin D and rifamycin. Labelling experiments also show that the protein begins to be synthesized early in sporulation. Examination of the ability of asporogenous mutants to produce cross-reacting material indicates that some event in stage II of sporulation determines its production.