Practice question

Endospore formation among Firmicutes is strategy for persistence when environmental conditions deteriorate, occurring specifically upon entry to stationary phase. Triggered by nutrient limitation, high cell density quorum peptides Phr, ComX, accumulation of guanosine tetraphosphate ppGpp produced by RelA SpoT. Phosphorelay KinA to KinE autophosphorylate and transfer to Spo0F to Spo0B to Spo0A, master transcription factor. Phosphorylated Spo0A activates genes for asymmetric polar septum via SpoIIE phosphatase dephosphorylating SpoIIAA leading to FtsZ relocation. Forespore compartment trapped chromosome only one third initially, translocated by SpoIIIE DNA motor. Engulfment proceeds by mother cell membrane phagocytosing forespore, then cortex peptidoglycan between double membranes, germ cell wall, dipicolinic acid calcium complex dehydrating core, SASPs binding DNA protecting from UV. Mother cell lysis releases mature spore. This lengthy ATP demanding program requires still functional metabolism, so initiation must occur early stationary, not death, when energy reserves remain sufficient to complete spore assembly and resist environmental insults.