Analysis of the Relationship Between the Decrease in pH and Accumulation of 3-Phosphoglyceric Acid in Developing Forespores of Bacillus Species

摘要

Analysis of the pH decrease and 3-phosphoglyceric acid (3PGA) accumulation in theforespore compartment of sporulating cells of Bacillus subtilis showed that the pH decrease of 1 to 1.2 units at approx 4 h of sporulation preceded 3PGA accumulation, as observed previously in B. megaterium. These data, as well as analysis of the forespore pH decrease in asporogenous mutants of B. subtillis, indicated that omega(G)-dependent forespore transcription, but not omega(K)-dependent mother cell transcription, is required for the forespore pH decrease. Further analysis of these asporogenous mutants showed an excellent correlation between the fore spore pH decrease and the forespore's accumulation of 3PGA. These latter results are consistent with our previous suggestion that the decrease in forespore pH results in greatly decreased activity of phosphoglycerate mutase in the forespore, which in turn leads to 3PGA accumulation. In further support of this suggestion, we found that (1) elevating the pH of developing forespores of B. megaterium resulted in rapid utilization of the forespore's 3PGA depot and (2) increasing forespore levels of PGM approx. 1O-fold in B. subtills resulted in a large decrease in the spore's depot of 3PGA. The B. subtilis strain with a high phosphoglycerate mutase level sporulated, and the spores germinated and went through outgrowth normally, indicating that forespore accumulation of a large 3PGA depot is not essential for these processes.