DORMANCY OF BACTERIAL ENDOSPORES: REGULATION OF ELECTRON TRANSPORT BY DIPICOLINIC ACID

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Abstract
The rate of O2 uptake in the presence of glucose or reduced diphosphopyridine nucleotide (DPNH) by cell-free extracts of Bacillus cereus var. terminalis is stimulated by the addition of free dipicolinic acid (DPA) and versene. Glucose oxidation was inhibited by Mn++, Ag+, Co++, Zn++, Cu++, Hg++ and Pb++, the inhibition being reversed by DPA. Mn++ inhibition was reversed adenosine diphosphate (ADP) and inorganic phosphate. A Ca++-activated adenosine triphos-phatase (ATPase) was detected in spore extracts the activity of which was stimulated 30% by 8 x 10-3 MDPA. Attempts to demonstrate a dependence of respiration on ATPase activity or adenosine diphosphate levels was negative. A soluble DPA-stimulated DPNH cytochrome c reductase was extracted from spores and vegetative cells. The enzyme is inhibited by versene and unaffected by 8-hydroxyquinoline. The specific stimulatory effect of DPA could not be attributed to the removal of an inhibitory ion. The possible role of divalent ions and DPA in regulating the respiratory dormancy of spores is discussed.