Crystallomycin revisited after 60 years: aspartocins B and C.

The study of an archived sample of crystallomycin complex using HPLC, ESI HRMS, and 2D NMR showed that two major components of the antibiotic, compounds 1 and 2, are lipopeptides having the same peptide core, Asp1-cyclo(Dab2-Pip3-MeAsp4-Asp5-Gly6-Asp7-Gly8-Dab9-Val10-Pro11-), N-acylated either with Δ3-iso-tetradecenoyl or Δ3-anteiso-pentadecenoyl that are identical to aspartocins C and B, respectively. According to the 2D NMR study, compound 2 in DMSO solution exists as a mixture of four conformers. The producing strain was identified as Streptomyces griseorubens. Compounds 1 and 2 have considerable Ca2+-dependent activity against Gram-positive bacteria including five MRSA strains.

New natural products identified by combined genomics-metabolomics profiling of marine Streptomyces sp. MP131-18.

Marine actinobacteria are drawing more and more attention as a promising source of new natural products. Here we report isolation, genome sequencing and metabolic profiling of new strain Streptomyces sp. MP131-18 isolated from marine sediment sample collected in the Trondheim Fjord, Norway. The 16S rRNA and multilocus phylogenetic analysis showed that MP131-18 belongs to the genus Streptomyces. The genome of MP131-18 isolate was sequenced, and 36 gene clusters involved in the biosynthesis of 18 different types of secondary metabolites were predicted using antiSMASH analysis. The combined genomics-metabolics profiling of the strain led to the identification of several new biologically active compounds. As a result, the family of bisindole pyrroles spiroindimicins was extended with two new members, spiroindimicins E and F. Furthermore, prediction of the biosynthetic pathway for unusual α-pyrone lagunapyrone isolated from MP131-18 resulted in foresight and identification of two new compounds of this family - lagunapyrones D and E. The diversity of identified and predicted compounds from Streptomyces sp. MP131-18 demonstrates that marine-derived actinomycetes are not only a promising source of new natural products, but also represent a valuable pool of genes for combinatorial biosynthesis of secondary metabolites.

Chemical modification and biological evaluation of new semisynthetic derivatives of 28,29-Didehydronystatin A1 (S44HP), a genetically engineered antifungal polyene macrolide antibiotic.

Twenty-three new derivatives of the heptaene nystatin analogue 28,29-didehydronystatin A(1) (1) (S44HP) were obtained by chemical modification of C16 carboxyl and amino groups of mycosamine. These derivatives comprised 15 carboxamides, 4 N-alkyl derivatives, 3 N-derivatives containing additional N-linked monosaccharide or disaccharide moiety (products of Amadori rearrangement), and 1 N-aminoacyl derivative. The derivatives have been tested in vitro against yeasts Candida albicans, Cryptococcus humicolus, and filamentous fungi (molds) Aspergillus niger and Fusarum oxysporum, as well as for hemolytic activity against human erythrocytes. Structure-activity relationships for the compounds obtained are discussed. The most active and least hemolytic derivative 3-(N,N-dimethylamino)propylamide of S44HP (6) was tested for acute toxicity and antifungal activity in animal model. Whereas amphotericin B and S44HP were active in vivo at doses close to the maximal tolerated dose, 6 was considerably less toxic and more active compared to these two antibiotics.

Cell wall teichoic acids of streptomycetes of the phenetic cluster 'Streptomyces fulvissimus'.

Structures of the anionic polymers of streptomycetes Streptomyces fulvissimus VKM Ac-994(T), Streptomyces longispororuber VKM Ac-1735(T), Streptomyces aureoveticillatus VKM Ac-48(T) and Streptomyces spectabilis INA 00606 belonging to the phenetic cluster 'S. fulvissimus' were investigated by chemical and NMR spectroscopic methods. A teichoic acid from the cell wall of S. spectabilis INA 00606 was studied in more detail, and this was shown to represent 1,3-poly(glycerol phosphate) substituted with glucosamine (alpha-D-GlcNAc) and L-glutamic acid (non-stoichiometric substitution). For the first time, glutamic acid is identified as an acyl substituent in teichoic acids of streptomycetes. The polymer chain is built of the following fragments: Cell walls of other streptomycetes of the phenocluster under study contain 1,3-poly(glycerol phosphates) with glucosamine as a glycosyl substituent at O-2 of the glycerol phosphate units and L-glutamic acid and lysine as O-2 acyl substituents. Not all amino sugar residues in the polymers of these strains are N-acetylated, and the content of the glucosamine and lysine residues in the polymers of different strains is not the same. Despite certain quantitative differences in the structures of the polymers, one may consider streptomycetes of the phenocluster 'S. fulvissimus' as closely related microorganisms, the details of the structures serving as additional criteria for the determination of the species status of a strain under study.