ANALYSIS OF THE RELATIONSHIP BETWEEN THE DECREASE IN PH AND ACCUMULATION OF 3-PHOSPHOGLYCERIC ACID IN DEVELOPING FORESPORES OF BACILLUS SPECIES

Analysis of the pH decrease and 3-phosphoglyceric acid (3PGA) accumula tion in the forespore compartment of sporulating cells of Bacillus sub tilis showed that the pH decrease of 1 to 1.2 units at similar to 4 h of sporulation preceded 3PGA accumulation, as observed previously in B . megaterium. These data, as well as analysis of the forespore pH decr ease in asporogenous mutants of B. subtilis, indicated that sigma(G)-d ependent forespore transcription, but not sigma(K)-dependent mother ce ll transcription, is required for the forespore pH decrease. Further a nalysis of these asporogenous mutants showed an excellent correlation between the forespore 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 activi ty of phosphoglycerate mutase In the forespore, which in turn leads to 3PGA accumulation. In further support of this suggestion, me found th at (i) elevating the pH of developing forespores of B. megaterium resu lted in rapid utilization of the forespore's 3PGA depot and (ii) incre asing forespore levels of PGM similar to 10-fold in B. subtilis result ed in a large decrease in the spore's depot of 3PGA. The B. subtilis s train with a high phosphoglycerate mutase level sporulated, and the sp ores germinated and went through outgrowth normally, indicating that f orespore accumulation of a large 3PGA depot is not essential for these processes.