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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 Δ 3 -iso-tetradecenoyl or Δ 3 -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 Ca 2+ -dependent activity against Gram-positive bacteria including five MRSA strains.

Probiotic strain Bacillus subtilis 534 is the base of sporobacterin, a pharmaceutical. In submerged culture it showed antibiotic activity against many of gram-positive and gram-negative bacteria and fungi. The spectrum of the antimicrobial activity of the culture fluid depended on the.cultivation time and aeration intensity. It was shown that component No. 1 of the antibiotic complex was effective against clinical isolates of Acinetobacter baumannii: 20 out of 24 isolates were susceptible to component No. 1, including 15 strains out of 16 panresistant isolates.

The fungal strain INA 01108 producing antibiotic substances with broad spectrum of antibacterial activity was isolated from the natural environment. By the morphological characteristics and DNA analysis it was shown to belong to Ascomycetes of Sordariomycetes. In submerged culture the strain produced at least four antibiotics. The major component of them was identified as eremophilane-type sesquiterpene eremoxylarin A. Eremoxylarin A is effective in vitro against grampositive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin group glycopeptide antibiotics resistant Leuconostoc mesenteroides VKPM B-4177. The efficacy and toxicity of eremoxylarin A was determined on a murine staphylococcal sepsis model. The dose of 6.25 mg/kg provided 100% recovery and survival of the animals, while the dose of 3.12 mg/kg was close to the ED50. The chemical structure of eremoxylarin A allows to modify the antibiotic and such studies may be relevant to design a less toxic derivative without loss of the valuable antimicrobial properties.

We demonstrate that the antibiotic amicoumacin A (AMI) is a potent inhibitor of protein synthesis. Resistance mutations in helix 24 of the 16S rRNA mapped the AMI binding site to the small ribosomal subunit. The crystal structure of bacterial ribosome in complex with AMI solved at 2.4 Å resolution revealed that the antibiotic makes contacts with universally conserved nucleotides of 16S rRNA in the E site and the mRNA backbone. Simultaneous interactions of AMI with 16S rRNA and mRNA and the in vivo experimental evidence suggest that it may inhibit the progression of the ribosome along mRNA. Consistent with this proposal, binding of AMI interferes with translocation in vitro. The inhibitory action of AMI can be partly compensated by mutations in the translation elongation factor G., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Two Bacillus subtilis strains isolated from the fruiting body of a basidiomycete fungus Pholiota squarrosa exhibited a broad range of antibacterial activity, including those against methicillin-resistant Staphylococcus aureus INA 00761 (MRSA) and Leuconostoc mes6nteroides VKPM B-4177 resistant to glycopep-> tide antibiotics, as well as antifungal activity. The strains were identified as belonging to the "B. subtilis" com- plex based on their morphological and physiological characteristics, as well as by sequencing of the 16S rRNA gene fragments. Both strains (INA 01085 and INA 01086) produced insignificant amounts of polyene antibiotics (hexaen and pentaen, respectively). Strain INA 01086 produced also a cyclic polypeptide antibiotic containing Asp, Gly, Leu, Pro, Tyr, Thr, Trp, and Phe, while the antibiotic of strain INA 01085 contained, apart from these, two unidentified nonproteinaceous amino acids. Both polypeptide antibiotics were new compounds efficient against gram-positive bacteria and able to override the natural bacterial antibiotic resistance.

Intraspecies fusion of protoplasts of two strains of Streptomyces fradiae, i.e native protoplasts of an inactive strain INA 00708 and heat inactivated protoplasts of a neomycin-producing strain ATCC 10745, and regeneration of the protoplasts of the inactive strain INA 00708 resulted in formation of clones producing neomycin and clones synthesizing antibiotics of an unknown nature differing from neomycin. All the active clones were unstable and lost their antibiotic activity in subcultures. Regeneration of the protoplasts of 4 different inactive strains of Streptomyces sp. also resulted in formation of active clones which were unstable and lost their capacity for the antibiotic synthesis after the first subculture. The data in principal indicate to the possible use of protoplast fusion and regeneration in screening of cultures producing new antibiotics among inactive strains of streptomycetes. However, the efficiency of such procedures is low since the experiments are labor-consuming and the resulting active clones are genetically unstable.

Interspecies fusion of protoplasts of the Streptomyces fradiae strains producing neomycin (an aminoglycoside antibiotic) and tylosin (a macrolide antibiotic) was performed with a view to isolate strains producing novel antibiotics. Fusion of the protoplasts of the neomycin- and tylosin-producing strains labelled by the resistance to monomycin and lincomycin, respectively, caused no formation of stable strains producing antibiotics differing in chromatographic mobility from the antibiotics produced by the initial strains. In fusion of the protoplasts of the unlabelled strains, heat-inactivated protoplasts of the active line of one strain (donor) and native protoplasts of the inactive line of the other strain (recipient) were used. When the neomycin-producing culture was used as a recipient the fusion led to formation of strain 195-34 producing antibiotics of the benzo(a)anthraquinone group. One of these antibiotics, i.e. antibiotic 34-I, proved to be a novel biologically active substance. After regeneration of the protoplasts of the initial strains, no stable strains producing antibiotics differing from neomycin and tylosin were isolated.

The method of total DNA restriction finger prints was applied to the study of Streptomyces monomycini INA 1465 producing monomycin, Streptomyces kanamyceticus INA K-13 producing kanamycin and strain 344 isolated after fusion of the protoplasts of strain 1465 and K-13, which produced albofungin and chloralbofungin, aminoglycoside antibiotics. For preparing the finger prints of the strains splitting by endonucleases BamHI, PstI, PvuII, and BgIII was used. The finger prints showed that strain 344 was related to the strain of S. monomycini and markedly differed from the strain of S. kanamyceticus. Strain 344 was likely to result from reconstruction (probably 20-kb deletion) of the genome of S. monomycini INA 1465 induced by the preparation and regeneration of its protoplasts. The reconstruction could affect the genome area with localization of the genes involved in monomycin biosynthesis and monomycin resistance genes.

Strain 344 synthesizing an antibiotic complex was isolated after fusion of the protoplasts of Streptomyces monomycini producing monomycin and Streptomyces kanamyceticus producing kanamycin. The major component of the complex was identified with albofungin and the minor one was suggested to be chloralbofungin. In the cultures of strain 344 variants forming monomycin were detected. After regeneration of the protoplasts of the parent strains there were isolated no stable clones synthesizing antibiotics differing from monomycin and kanamycin.

Production of the nebramycin complex in Streptomyces cremeus subsp. tobramycini before and after the protoplast formation and regeneration was comparatively studied. The antibiotic production was estimated by the total activity and component composition of the nebramycin complex. It was found that formation and regeneration of the protoplast led to lowering of the activity and changing of the complex component composition. Strains mainly synthesizing each one of the three basic components of the nebramycin complex were isolated. The strains proved to be unstable by the antibiotic production property and after three subcultures lost the differences in the complex component composition.