Biochemical Changes and their Regulation during Spore Formation and Germination

摘要

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.