Produces a 42-residue extracellular sporulation delaying protein (SDP) that collapses the proton motive force (probably both the membrane potential and pH gradient) across the cell membrane, which leads to autolysis; may form a proton channel (PubMed:22469514). Induces the lysis of other B.subtilis cells that have not entered the sporulation pathway, inducing cannibalism to provide a source of nutrients to support sporulation, and at the same time delaying commitment to the energetically expensive and irreversible onset of sporulation (PubMed:12817086). Addition of SDP to liquid cultures halts growth, leads to increased cell permeability and eventually cell lysis in a significant subset of the population, although some cells survive and resume growth after a lag period (PubMed:20805502). Effects of SDP are irreversible within 10 minutes (PubMed:22469514). Addition of SDP to solid cultures induces killing, it is much more effective than SKF (AC O31422) (PubMed:20805502). Has antibiotic action against Gram-positive Firmicutes (L.acidophilus, M.megaterium, P.polymyxa, S.aureus, S.epidermidis) but not Actinobacteria M.luteus or Gram-negative P.aeruginosa or K.pneumoniae (PubMed:20805502, PubMed:22469514). SDP induces expression of the sdpR-sdpI operon (PubMed:12817086). Its maturation is dependent on SdpA and SdpB. Also functions as a ligand, binds to SdpI triggering a signal transduction cascade that protects the cell against the toxic effects of its own SDP. Proprotein probably interacts with chaperone CsaA. Produces a secreted protein originating from this gene (PubMed:12817086), secreted by the general secretory pathway (PubMed:14568161). By Spo0A during nutrient starvation, through its direct negative control of AbrB (PubMed:12817086). Repressed by AbrB during regular growth when nutrients are plentiful, in association with the transcriptional repressor Abh (PubMed:17720793). Protein not detected during exponential growth, accumulates during stationary phase (at protein level) (PubMed:14568161). Production of active SDP (able to induce SdpI and kill cells) is a multi-step process that requires signal peptide cleavage (probably by SipS or SipT) (PubMed:14568161) as well as SdpA and SdpB. The disulfide bond is not required for maximum toxicity (PubMed:23687264). Includes a disulfide bond. When the sdpA-sdpB-sdpC operon is deleted, increased rate of spore formation; a double operon deletion (sdpA-sdpC plus skfA-skfH) makes spores even faster (PubMed:12817086). In a single gene deletion no SDP is produced (PubMed:20805502, PubMed:23687264). I'll have you for supper - Issue 90 of January 2008