Cerein 7B is a new bacteriocin produced simultaneously with cerein 7A by Bacillus cereus Bc7 in liquid brain heart infusion cultures. Both bacteriocins are not synergistic. The two peptides have been purified to homogeneity by hydrophobic interaction, cation exchange and reverse-phase liquid chromatography. They can be distinguished by their N-terminal amino acid sequences N-Gly-Trp-Gly-Asp-Val-Leu (7A) and N-Gly-Trp-Trp-Asn-Ser-Trp-Gly-Lys (7B). Pre-cerein 7B is 74 amino acids long and contains an 18 aminoacid double-glycine type leader sequence that is removed to produce the mature bacteriocin. The leader peptide sequence is related to that of sec-independent secretion signals suggesting that cerein 7B belongs to class II sec-independent bacteriocins.