Biochemical Changes and their Regulation during Spore Formation and Germination.

Abstract

Abstract : Metabolism of several important small molecules has been examined during sporulation and spore germination in Bacillus megaterium. These studies have indicated (1) the major known low molecular weight thiol/disulfide in Bacillus species is Coenzyme A (CoA); (2) CoA in growing or sporulating cells is in either an acyl form or as the free thiol, but that in dormant spores about 75% is in a disulfide form with 50% in disulfide linkage to spore core proteins; these disulfides are cleaved in the first minutes of spore germination; (3) dormant spores contain an NADH-linked disulfide reductase which cleaves CoA disulfides. This enzyme is low or absent from log-phase or early sporulating cells, and appears during sporulation. It has no activity on cystine, glutathione or pantethine, and has highest activity on 4',4''-phosphopantethine; (4) Bacillus megaterium cells contain a very low level of cyclic GMP (cGMP), but cGMP is not found in spores and it appears unlikely to be a modulator of sporulation, germination or outgrowth; (5) The pH within dormant spores is about 6.3, a value which is independent of the external pH. However, early in spore germination the internal pH rises to 7.5; and (6) the key enzyme in regulation of 3-phosphoglycerate (3-PGA) accumulation during sporulation, and its rapid utilization during spore germination (and thus ATP production) is PGA mutase.