Chemical and Morphological Studies of Bacterial Spore Formation

Abstract

The development of both the spore and parasporal protein crystal of Bacillus cereus var. alesti was followed using chemical and cytological techniques. The changes which led to the formation of the fore-spore were similar to those already described for Bacillus cereus. However, adjacent to the developing fore-spore a small inclusion became discernible in phase contrast. This protein inclusion during its growth was differentiated from the chromatln and lipid-containing inclusions by sequential staining techniques.During spore and crystal formation no net synthesis of either nucleic acid was detected. Tracer studies with radioactive phosphorus confirmed that the spore chromatin was derived from that in the vegetative cell. These same studies also indicated that a turnover of ribonucleic acid occurred during the sporulation process.During their formation both the spore and crystal incorporated methionine-asS from the medium and from cellular material into a bound form. Sequential extractions with alkali and with alkaline-thioglycollate reagent revealed that the solubility characteristics of the mature crystal were possibly related to the presence of intermolecular disulphide bonds which developed after the major synthesis of the crystal was complete.The synthetic nature of sporogenesis and crystal formation is discussed with reference to the concept of "endotrophic" sporulation.

Participation of the Cytoplasmic Membrane in the Growth and Spore Formation of Bacilli

“…As before (28,29), synchronously sporulating cultures greatly facilitated the interpretation of the development of this structure and its related appendages.…”

“…Previously, in sections cut from methacrylate embeddings, the initial spore septum appeared as a thin, single layer continuous with the inner surface of the cell wall (28,29). However, in sections cut from polyester embeddings the spore septum appears multi-layered.…”

“…A diagrammatic interpretation of this sequence of events is given in Fig. 9, A to H. The changes in chromatin arrangement have already been described (28,29); hence only the sporulating ends of the cell are shown. The steps A to D are somewhat tentative but do account for most of the arrangements seen in sections of the cells from the four cultures studied.…”

“…Then those small refractile granules which become sharply visible in living phase contrast smears and are presumably inclusions of ~-hydroxybutyrate polymer common to these bacilli showed rapid staining with Sudan black. In contrast to the mesosomes, these sudanophilic sites appear to have little affinity for osmium and are found as vacuoles in thin sections (29).…”

“…Recent studies of spore formation in members of the genus Bacillus have shown that, early in the process, a remarkable form of internal division occurs (28)(29). The initial wall of the forespore was first detected as a septum, apparently continuous with the cell wall and invaginating centrally from the inner surface, thus forming between it and the end of the cell, a pocket, into which the future spore chromatin is enclosed.…”