Produces a 26-residue extracellular sporulation filling factor (SKF) that induces the lysis of other B.subtilis cells that have not entered the sporulation pathway, providing 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, PubMed:20805502). Can also inhibit growth of other bacteria at high concentrations (PubMed:11851812). Addition of SKF to solid cultures induces killing, but it is much less effective than SDP (AC O34344) (PubMed:20805502). Has a role in protecting the secreted lipase LipA against proteolysis, either by modulating its folding or by acting as a protease inhibitor (PubMed:15812018). Probably secreted by the ABC transporter SkfEF. By Spo0A (PubMed:12817086) and PhoP (PubMed:16816204), during nutrient starvation, especially phosphate starvation. Repressed by AbrB during normal growth when nutrients are plentiful, in association with the transcriptional repressor Abh. This is a cyclic peptide (PubMed:20805502, PubMed:23282011). The first step in SKF maturation is probably thioether bond formation (PubMed:23282011). Cyclic, disulfide-containing sactipeptide with a thioether cross-link of cysteine to methionine. When the skfA-skfB-skfC-skfE-skfF-skfG-skfH 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 SKP is produced (PubMed:20805502). Accelerated cannibalism by skf- cells is seen on solid media but not in liquid media. I'll have you for supper - Issue 90 of January 2008