Biochemical studies of bacterial sporulation and germination. XIX. Phosphate metabolism during sporulation.

Acid-soluble phosphate compounds represent about 25 % of the total phosphate of Bacillus megaferium vegetative cells, but only 7% of the total phosphate in dormant spores. In vegetative cells, 12 compounds make up 90% of the acidsoluble phosphate. These same compounds predominate throughout growth and early sporulation, although their relative amounts change during the process. One hour before refractile spores appear within sporangia, 3-phosphoD-glyceric acid (PGA) becomes a major component of the sporangial pool and, with the appearance of refractile spores, PGA becomes more difficult to extract. PGA is the largest component of the acid-soluble phosphate pool of B. megaterium spores produced in rich as well as minimal media, and also predominates in Bacillus cereus and Bacillus subfilis spores. Spore PGA appears to be synthesized in a compartment which is inaccessible to inorganic phosphate in the medium, although, at the time of synthesis, Pi from the medium does enter the sporangium. PGA in dormant spores is very Crmly bound, and does not readily exchange with external PGA.