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Three new antibiotics, tridecaptins A, B and C, were isolated from culture broths of strains of Bacillus polymyxa AR-110, B-2 and E-23, respectively. All are acyl tridecapeptides differing from each other in the fatty acid components and amino acid residues. They are weakly active against Gram-negative and Gram-positive bacteria in vitro and in vivo.While screening for new antibiotics from the genus Bacillus, several new antibiotic substances belonging to a new class of antibiotics were found in culture broths of strains of Bacillus polyinyxa. As all are acyl tridecapeptides, "tridecaptin" is proposed as the class name for these antibiotics. To distinguish individual members, a capital letter is assigned in order of discovery. Tridecaptins B and C are complexes requiring resolution. When the individual components are separated appropriate suffixes will be assigned.In this report, the production, isolation and primary characterization of tridecaptins A, B and C are presented. The Producing OrganismsStrain AR-110 produces tridecaptin A, strain B-2 tridecaptin B, and strain E-23 tridecaptin C. The three strains are closely related to each other, and are judged to belong to Bacillus polymyxa based on taxonomic studies. The taxonomic characteristics of these strains are as presented for strain E-23.A. Morphology (2) Gly-IM-agar slant (30°C, 1-7 days) : Growth moderate, beaded to echinulate, whitish gray, surface shiny (at 1 day) changing to dull after 2 days. Gummy consistency and opaque density. Diffusible and non-diffusible pigments are not observed.* Gly-IM-agar:Glycerol 0 .5y., peptone 0.25%, beef extract 0.25%, yeast extract 0.25%, NaCI 0.3%, agar 1.25 %, pH 6.8.

Thielocins A2a, A2/?, A3, Bl, B2 and B3 were isolated as a novel family of phospholipase A2 inhibitors from the fermentation broth of Thielavia terricola RF-143together with thielavins and thielocins Ala and Al/?. The most potent inhibitory activity (IC50 =0.0033^) against rat group II phospholipase A2 was shown by thielocin Al/?. Against human group II phospholipase A2, thielocin B3 (IC50 =0.076 ijm) was the most potent.Phospholipase A2 (PLA2) is a lipolytic enzyme which hydrolyzes the sn-2 fatty acyl ester bond ofphospholipids to produce free fatty acids and lysophospholipids1}.It

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