Saccharothrix algeriensis NRRL B-24137, the first non-Streptomyces actinobacterium, produces holomycin after cystine feeding.

Saccharothrix algeriensis NRRL B-24137 is an actinobacterium isolated from Algerian Saharan soil. This strain has the ability to produce several dithiolopyrrolone antibiotic derivatives depending on the precursors added to the culture medium. This group of antibiotics is known for their potent antimicrobial and anticancer activities. Holomycin is a member of the dithiolopyrrolone group of antibiotics, and has already been isolated from several species of actinobacteria belonging to the genus Streptomyces and also from some Gram-negative bacteria. In this study, holomycin was produced for the first time in the culture broth of a non-Streptomyces actinobacteria. This antibiotic was induced by adding 5 mM of L-cystine as precursor to the semi-synthetic fermentation broth of Sa. algeriensis NRRL B-24137 and then fully identified after HPLC purification. The minimum inhibitory concentrations (MIC) of holomycin were determined against several pathogenic microorganisms, including Escherichia coli ATCC 10536 Klebsiella pneumoniae CIP 82.91, Listeria monocytogenes CIP 82110, Staphylococcus aureus CIP 7625, Aspergillus carbonarius M333, Fusarium culmorum FC1, Candida albicans IPA 200. This antibiotic showed a broad-spectrum antimicrobial activity, inhibiting a variety of Gram-positive and Gram-negative bacteria, and micro-fungi.

New dithiolopyrrolone antibiotics induced by adding sorbic acid to the culture medium of Saccharothrix algeriensis NRRL B-24137.

Dithiolopyrrolone antibiotics, produced by several microorganisms, are known for their strong antimicrobial activities. This class of antibiotics generated new interest after the discovery of their anticancer and antitumor properties. In this study, four new antibiotics were purified from the fermentation broth of Saccharothrix algeriensis NRRL B-24137 and characterized as dithiolopyrrolone derivatives. These new dithiolopyrrolone antibiotics were induced by adding sorbic acid, as precursor, at a concentration of 5 mM to the semi-synthetic medium. The analysis of the induced antibiotics was carried out by HPLC. The maximal production of the antibiotics PR2, PR8, PR9 and PR10 was 0.08±0.04, 0.21±0.04, 0.13±0.03 and 0.09±0.00 mg L(-1) , respectively, obtained after 8 days of fermentation. The chemical structures of these antibiotics were determined by (1) H- and (13) C-nuclear magnetic resonance, mass and UV-visible data. The four new dithiolopyrrolone antibiotics - PR2, PR8, PR9 and PR10 - were characterized, respectively, as crotonyl-pyrrothine, sorbyl-pyrrothine, 2-hexonyl-pyrrothine and 2-methyl-3-pentenyl-pyrrothine. The minimum inhibitory concentrations of the new induced antibiotics were determined.

Dithiolopyrrolone antibiotic formation induced by adding valeric acid to the culture broth of Saccharothrix algeriensis.

Three new antibiotics were isolated from the fermentation broth of Saccharothrix algeriensis NRRL B-24137 and characterized as the dithiolopyrrolone derivatives valerylpyrrothine (1), isovalerylpyrrothine (2), and formylpyrrothine (3) as well as the known antibiotic aureothricin. The production of the dithiolopyrrolone derivatives was induced by adding valeric acid to the culture medium. The compounds exhibited moderate antimicrobial activity in vitro.