Where and why have so many metabolic enzymes gone from developing spores of Bacillus subtilis?

Developing spores (forespores) of Bacillus subtilis lack TCA cycle and amino acid and ribonucleotide biosynthetic enzymes but still carry out much macromolecular synthesis to make a spore-but how and why? Work by many showed that the mother cell supplies ATP and metabolites to the forespore via a feeding tube. Two recent studies in this issue of Genes & Development, by Massoni and colleagues (doi:10.1101/gad.352498.124) and Riley and colleagues (doi:10.1101/gad.352535.124), now show that specific metabolic enzymes disappear early in forespore development via proteolysis by ClpCP and a forespore-specific activator termed MdfA. Future work may clarify how this proteolysis recognizes specific metabolic enzymes and determine the advantages of this overall process for spores.