Samarosporin, a new peptide antibiotic. I. Fermentation, isolation and characterization.

Abstract

A new antibiotic, samarosporin, was isolated in a crystalline state from a mycelial extract of a strain of Samarospora species (an ascomycete). Samarosporin is a neutral cyclopeptide and has a molecular formula of C12H111N15O19. Samarosporin shows a broad antimicrobial activity against various test microorganisms. A fungal strain No. F-7762 isolated from a soil sample was found to belong to the genus Samarospora of Ascomycetes. A cyclopeptide antibiotic was produced in the mycelium of the strain, and the compound was named samarosporin. The samarosporin-producing strain has been deposited in the Fermentation Research Institute, Chiba, Japan, with accession number FERM-P 224. The taxonomic study of the producing strain of the fungus will be reported in a separate paper.

The crystal structure of samarosporin I at atomic resolution

“…Samarosporin was originally isolated from a methanol/water extract of the mycelium of a large‐scale fermentation of strain F‐7762 of a species of the ascomycetous fungus Samarospora rostrup . The crude peptide was crystallized from methanol solutions by addition of acetone and recrystallized from methanol . A sample (kindly provided by Dr N. Inoue from the Research Institute, Daiichi Seiyaku Co., Ltd, Tokyo) was further chemically characterized and the sequences of the major and minor components (I and II) established .…”

“…To date, crystal structures of the 16‐residue SF2 peptaibols antiamoebin and cephaibols A, B, and C have been determined . The 15‐residue peptide antibiotic sam was isolated from a species of the ascomycetous fungus Samarospora rostrup . Its main component sam I, accounting for 88% of the peptide produced, was found to be identical with the peptaibols stilbellin I from a species of Stilbella , emerimicin IV from Emericellopsis microspora , and is closely related to heptaibin , which was isolated together with emerimicin IV, from a species of Emericellopsis .…”

A natural, single-residue substitution yields a less active peptaibiotic: the structure of bergofungin A at atomic resolution

“…The bacterial growth assay in agar diffusion (described in detail in the Supporting Information) shows that bergofungin at 1 mg ml À1 is not active against Staphylococcus aureus, Escherichia coli and Candida albicans, whereas samarosporin at 156 mg ml À1 is active against S. aureus and at 625 mg ml À1 is active against E. coli and C. albicans (data from Inoue et al, 1976). Furthermore, 1 mg ml À1 bergofungin solution has no effect against Pseudomonas aeruginosa, while samarosporin is active against Gram-positive and Gram-negative bacteria, yeasts, fungi and protozoa at lower concentrations.…”

ChemInform Abstract: Peptaibiomics: Towards a Myriad of Bioactive Peptides Containing Cα‐Dialkylamino Acids?

“…[48], which later deceased; Trichotoxin A (TXT A) from Trichoderma viride NRRL 5242 and Trichotoxin B (TXT B) from Trichoderma viride NRRL 5243, two secondary invaders of maize cultures infested with Helminthosporium maydis ( ¼ Bipolaris maydis, teleomorph Cochliobolus heterostrophus) race T, the causal agent of Southern Leaf Spot of Maize [49]; Emerimicins I -IV from Emericellopsis microspora 333 [50]; Zervamicins I and II from Emericellopsis salmosynnemata 336 [51]; Samarosporin from a mycelial culture of the ascomycete Samarospora sp. FERM-P 224 (F-7762) [52] that ceased the production of the antibiotic and is no longer deposited.…”