Identification and Characterization of Two Novel Clostridial

Two novel antibacterial peptides of clostridial species were purified, N-terminally sequenced, and charac-terized. Moreover, their structural genes were identified. Closticin 574 is an 82-amino-acid bacteriocin pro-duced by Clostridium tyrobutyricum ADRIAT 932. The supernatant of the producing strain showed a high level of activity against the indicator strain C. tyrobutyricum. The protein is synthesized as a preproprotein that is possibly secreted via the general secretion pathway, after which it is hydrolyzed at an Asp-Pro site. Circularin A is produced by Clostridium beijerinckii ATCC 25752 as a prepeptide of 72 amino acids. Cleavage of the prepeptide between the third leucine and fourth valine residues followed by a head-to-tail ligation between the N and C termini creates a circular antimicrobial peptide of 69 amino acids. The unusually small circularin A leader peptide of three amino acids is cleaved off in this process. The supernatant of C. beijerinckii ATCC 25752 showed a broad antibacterial activity range. Clostridia have a negative image as many species are known as pathogens (50), toxin producers (50), and food-spoilage bacteria (36). Various clostridia produce bacteriocins, but de-spite their long history as a means of typing clostridia (33, 39), only little sequence, functional, or structural information i