A limited number of antibiotics can be used against Helicobacter pylori infection, and resistance jeopardizes the success of treatment. Therefore, a search for new agents is warranted. The use of probiotics to enhance gastrointestinal health has been proposed for many years, but the scientific basis of the prophylactic and therapeutic actions of probiotics has not yet been clearly delineated. Probiotic strain Bacillus subtilis 3, whose safety has previously been demonstrated, is known to have antagonistic properties against species of the family Enterobacteriaceae. In the present study, it was also found to inhibit H. pylori. The anti-H. pylori activity present in the cell-free supernatant was not related to pH or organic acid concentration. It was heat stable and protease insensitive. At least two antibiotics, detected by thin-layer chromatography (R f values, 0.47 and 0.85, respectively) and confirmed by high-performance liquid chromatographic analysis, were found to be responsible for this anti-H. pylori activity. All H. pylori strains tested were sensitive to both compounds. One of these compounds was identified as amicoumacin A, an antibiotic with anti-inflammatory properties. MICs for H. pylori determined in solid and liquid media ranged between 1.7 and 6.8 g/ml and 0.75 and 2.5 g/ml, respectively. The underestimation of MICs determined in solid medium may be due to physicochemical instability of the antibiotic under these test conditions. An additive effect between amicoumacin A and the nonamicoumacin antibiotic against H. pylori was demonstrated.

A plasmid-linked antimicrobial peptide, named coagulin, produced by Bacillus coagulans I 4 has recently been reported (B. Hyronimus, C. Le Marrec and M. C. Urdaci, J. Appl. Microbiol. 85:42-50, 1998). In the present study, the complete, unambiguous primary amino acid sequence of the peptide was obtained by a combination of both N-terminal sequencing of purified peptide and the complete sequence deduced from the structural gene harbored by plasmid I 4 . Data revealed that this peptide of 44 residues has an amino acid sequence similar to that described for pediocins AcH and PA-1, produced by different Pediococcus acidilactici strains and 100% identical. Coagulin and pediocin differed only by a single amino acid at their C terminus. Analysis of the genetic determinants revealed the presence, on the pI 4 DNA, of the entire 3.5-kb operon of four genes described for pediocin AcH and PA-1 production. No extended homology was observed between pSMB74 from P. acidilactici and pI 4 when analyzing the regions upstream and downstream of the operon. An oppositely oriented gene immediately dowstream of the bacteriocin operon specifies a 474-amino-acid protein which shows homology to Mob-Pre (plasmid recombination enzyme) proteins encoded by several small plasmids extracted from grampositive bacteria. This is the first report of a pediocin-like peptide appearing naturally in a non-lactic acid bacterium genus.Bacteriocins are ribosomally synthesized antimicrobial polypeptides that are usually inhibitory only to strains closely related to the producing bacteria. These antimicrobial compounds are thought to provide the producer strain with a selective advantage over other strains. Bacteriocins produced by gram-positive bacteria are often membrane-permeabilizing cationic peptides with fewer than 60 amino acid residues (25,29). In recent decades, the major advances in this field have been made in the lactic acid bacterium (LAB) family, due to the eminent economic importance of these microorganisms. Hence, the great structural diversity of LAB bacteriocins in combination with the fact that many bacteriocin producing LAB are present in a variety of naturally fermented food and feed products has led to a great interest in the potential of these bacteria as biopreservatives that could, at least partially, replace chemical preservatives (50). The bacteriocins of LAB have been divided into four distinct classes by biochemical and genetic means (28,29). Bacteriocins of class I and II are by far the most studied because they are both the most abundant ones and the most prominent for industrial application (41). Class I bacteriocins called lantibiotics contain modified amino acid residues, lanthionine and methyllanthionine, which are formed posttranslationally (10). Class II consists of bacteriocins that lack modified residues. The pediocin-like bacteriocins constitute a large subgroup within class II: they are all small, heat-stable, membrane-active peptides that have a YGN GVXC consensus motif and are also characterized by their strong inh...

Streptomyces strain K1-02, which was identified as a strain of Streptomyces albidoflavus, secreted at least six extracellular proteases when it was cultured on feather meal-based medium. The major keratinolytic serine proteinase was purified to homogeneity by a two-step procedure. This enzyme had a molecular weight of 18,000 and was optimally active at pH values ranging from 6 to 9.5 and at temperatures ranging from 40 to 70°C. Its sensitivity to protease inhibitors, its specificity on synthetic substrates, and its remarkably high level of NH2-terminal sequence homology with Streptomyces griseus protease B (SGPB) showed that the new enzyme, designated SAKase, was homologous to SGPB. We tested the activity of SAKase with soluble and fibrous substrates (elastin, keratin, and type I collagen) and found that it was very specific for keratinous substrates compared to SGPB and proteinase K.

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