Mechanisms for Regulation of the Activity of Key Enzymes in Developing Dormant and Germinated Bacterial Spores

摘要

Highlights of research findings in the past three years are: (1) A novel enzyme which uses NADH to reduce disulfides (such as oxidized Coenzyme A) containing 4-phosphopantethine residues has been purified to homogeneity from Bacillus megaterium spores and characterized; it is a new member of the class of pyridine nucleotide dependent disulfide reductases. The enzyme is present in a number of gram positive spore formers, but not in gram negative bacteria or eukaryotic organisms. (2) The low pH (6.3-6.5) in the dormant spore core rises to approx. 7.5 in the first seconds of spore germination. This process is more rapid than dipicolinic acid release and is accompanied by a release of protons as well as other monovalent cations (K(+) and Na(+)) into the growth medium. (3) Using a mutant of B. sphaericus which cannot form spore cortex we have shown that spore cortex is not necessary for acquisition of UV light resistance or low molecular weight basic proteins by the developing spore. (4) The sequence specific spore protease of B. megaterium has been purified and characterized. It is synthesized during sporulation as a zymogen which is only processed to an active form later in sporulation. Identification of the zymogen form of this enzyme explains in part the regulation of this enzyme. and (5) Cyclic AMP was shown to be essentially absent from C. perfringens during all phases of its life cycle. Thus cAMP plays no role in regulating sporulation in this organism.