This family consists of the small acid-soluble spore proteins (SASP) of the H type (sspH). SspH are unique to spores of Bacillus subtilis and are expressed only in the forespore compartment during sporulation of this organism. The sspH genes are monocistronic and are recognised by the forespore-specific sigma factor for RNA polymerase - sigma-G. The specific role of this protein is unclear but is thought to play a role in sporulation under conditions different from that of the common laboratory tests of spore properties [1].

1: Regulation of four genes encoding small, acid-soluble spore proteins in Bacillus subtilis. Cabrera-Hernandez A, Sanchez-Salas JL, Paidhungat M, Setlow P; Gene 1999;232:1-10. PMID:10333516