Microbial metabolites were screened for a transcriptional up-regulator of low density lipoprotein (LDL) receptor by a reporter assay. TMC-49A was discovered as an up-regulator obtained from the fermentation broth of Streptomyces sp. AS1345. The structure of TMC-49A was elucidated to be butyl N-phenethylcarbamate by spectroscopic analyses. This compound enhanced the synthesis of LDL receptor in human hepatoma HepG2 cells as assessed by a receptor binding assay. Taxonomy of the producing strain is also described.

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A novel isochroman carboxylic acid CJ-12, 373 was isolated from Penicillium sp. CL22557. CJ-12, 373 inhibits both DNA gyrase-mediated supercoiling and relaxation without the formation of a cleavage intermediate, suggesting that CJ-12, 373 inhibits DNA gyrase at a stage distinct from the religation step. CJ-12, 373 is not selective for procaryotic DNA gyrase as it also inhibits relaxation mediated by eukaryotic topoisomerase II. The antimicrobial potency of CJ-12, 373, however, is largely attributed to its inhibition of DNA gyrase.

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Glisoprenins C, D, and E, new glisoprenin derivatives, were isolated together with glisoprenin A from submerged cultures of the deuteromycete Gliocladium roseum HA190-95. All glisoprenins inhibited appressorium formation in Magnaporthe grisea on inductive (hydrophobic) surfaces. The compounds exhibited moderate cytotoxic, but no antifungal, antibacterial or phytotoxic activities.

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A novel 19-membered macrocyclic lactam antibiotic, cremimycin, was isolated from the culture broth of an actinomycete strain. The producing organism, designated MJ635-86F5, was identified as a member of Streptomyces. Cremimycin was isolated from the mycelial cake by extraction with CHCl₃-MeOH and precipitation with hexane-MeOH. The structure of cremimycin was determined by spectroscopic study.
Cremimycin showed broad antimicrobial activities against Gram-positive bacteria including MRSA.

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A new antibiotic designated nothramicin was isolated from the culture broth of Nocardia sp. MJ896-43F17 which was closely related to Nocardia brasiliensis. It was isolated by the Diaion HP-20 column chromatography, butyl acetate extraction and purified by HPLC. It inhibited the growth of mycobacteria at the concentration of 1.56∼25 μg/ml. Nothramicin was revealed to be a new member of anthracycline antibiotics by the various spectroscopies.

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A novel 16-membered-ring macrolide agent (CP-163, 505, a reductive amination derivative of repromicin) was identified as an antibacterial against Pasteurella haemolytica, P. multocida and Actinobacillus pleuropneumoniae, important etiological agents of livestock respiratory disease. In vitro MIC_50/90 analysis revealed that CP-163, 505 was more potent (4×) than tilmicosin against P. multocida, and equivalent to tilmicosin against P. haemolytica and A. pleuropneumoniae. In time kill kinetic studies, CP-163, 505 showed bactericidal activity against P. haemolytica, P. multocida and A. pleuropneumoniae and bacteriostatic activity against E. coli at 8 times its MIC. In vitro, CP-163, 505 was more potent in alkaline pH (16∼32×) and less potent in the presence of excess cations (Mg⁺² and Ca⁺², 4×). EDTA and PMBN increased CP-163, 505 potency against E. coli (4×) but not against the other species. Similar results were obtained with erythromycin A and tilmicosin, which were used as controls. From our data, we hypothesize that Pasteurella and Actinobacillus have an outer membrane significantly different from that of the typical enteric Gram-negative bacterium E. coli.

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Eight novel quinolones with anti-Helicobacter pylori activity were isolated from the actinomycete Pseudonocardia sp. CL38489. The quinolones were very potent against H. pylori with MICs up to 0.1 ng/ml. The quinolones appear to be specific for H. pylori, since they did not show antimicrobial activity when tested against a panel of other micro-organisms.

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In the course of our screening program for artemisinin-like antimalarial compounds from microorganisms, seven fungal metabolites such as radicicol and heptelidic acid were identified as active compounds. Some of them exhibited antimalarial activity in vitro against the human malaria parasite Plasmodium falciparum to the extent of approximately 1/10 as potent as artemisinin. Radicicol was moderately active in vivo against Plasmodium berghei in mice.

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A versatile plasmid cloning vector pRL60 carrying kanamycin/neomycin resistance (km/neo), erythromycin resistance (ermE) and α-amylase (α-amy) marker genes that replicates in various Amycolatopsis mediterranei strains and Escherichia coli has been constructed. This cloning vector has been derived from a hybrid plasmid pRL50, which was developed by cloning ermE from pIJ4026 into a pRL1 derivative pULAM2. While cloning ermE into the BamHI site of pULAM2, only a hybrid plasmid pRL50 with an additional copy of pULAM2 was selected. Thus pRL50 (18.7 kb) contained two copies each of the km/neo, α-amy, and one copy of ermE. When pRL50 was transformed into A. mediterranei DSM 40773 through electroporation and selected under erythromycin resistance, the plasmid underwent a spontaneous deletion of 8.5 kb fragment resulting in the formation of plasmid pRL60. pRL60 (10.2 kb) is a shuttle vector between A. mediterranei and E. coli with three marker genes: km/neo, ermE and α-amy. ermE is expressed in A. mediterranei thus allowing good selection of transformants. The α-amy gene of pRL60 is also expressed in A. mediterranei DSM 40773 and its activity can be easily detected on starch containing medium after iodine staining. Most critical parameters evaluated for electrotransformation using pRL60 in A. mediterranei were growth phase, electrical field strength, pulse length, pretreatment of mycelia with lysozyme and use of salt free water. At optimized parameters, a transformation efficiency of 4.0×10⁴ transformants/μg DNA was reproducibly achieved for A. mediterranei DSM 40773. pRL60 could also be transformed into A. mediterranei DSM 43304, DSM 46095, MTCC-17 and in mutants F1/24 and T-195, (derived from an industrial strain of A. mediterranei N813). The α-amy of pRL60 conferred an amylolytic phenotype to all these strains. With the development of pRL60 and a reproducible transformation protocol, the application of recombinant DNA techniques to these industrial microorganisms has now become feasible.

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Peptaibols are linear α-aminoisobutyric acid-containing peptide antibiotics originating from soil fungi mainly of the genus Trichoderma and biosynthesized in complex mixtures of closely related analogues by a polyenzymatic pathway. Addition of amino acids such as α-aminoisobutyric acid (Aib), glutamic acid or arginine, to the fermentation medium of two Trichoderma strains, T. harzianum and T. longibrachiatum, has been shown to result in the simplification of the natural peptaibol mixtures, leading in each case to the almost exclusive biosynthesis of a single peptide. Surprisingly, the obtained peptides are Aib-enriched, whether the added amino acid is Aib, Glu or Arg. By adding Aib to the fermentation medium of T. harzianum, two new Aib-rich peptaibols were isolated. Moreover, adding glutamic acid to the culture medium of T. longibrachiatum, which produces both neutral and acidic 20-residue peptaibols with either glutamine or glutamic acid at position 18, increases the production of the acidic peptides. However, arginine which is a positively charged amino acid generally absent from peptaibol sequences, is not incorporated in trichorzins when added to the fermentation medium of T. harzianum.

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α-Aminoisobutyric acid-directed biosynthesis in two Trichoderma strains has been shown to lead to the simplification of the natural peptaibol microheterogeneous mixtures and to the production of new analogues. Hence, two new peptides originating from T. harzianum, trichorzin PA_U 4 and harzianin PC_U 4, were isolated by HPLC. Their sequences were determined by positive liquid secondary-ion mass spectrometry (LSI MS). Trichorzin PA_U 4 and harzianin PC_U 4 are 18- and 14-residue peptaibols, respectively, both containing a high proportion of α-aminoisobutyric acid (Aib). LSI MS performed with lithium cationized peptides, allowed to assign the relative position of leucine/isoleucine isomeric residues, even without the use of tandem mass spectrometry.

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Some derivatives of bactobolin were prepared from bactobolin (1) by radical reduction and formation of the fused azetidine ring. The derivatives proved less active than the parent antibiotic 1 against bacteria, indicating that dichloromethyl group at C-3 position play an important role in biological activity.

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TAN-1057A∼D, dipeptides isolated from bacteria Flexibacter sp. PK-74 and PK-176, are new antibiotics with potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). We describe, in detail, the synthesis of several TAN-1057A/B analogs by a convergent route featuring a new method to construct the cyclic amidinourea functional group. The biological activity of these substances against methicillin-resistant Staphylococcus aureus (MRSA) is reported.

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3-epi-Actinobolin was synthesized by the chemical transformation of actinobolin involving a key step of the reconstruction of fused δ-lacton skelton via intramolecular acylation reaction. The analogue with low toxicity weakly inhibits Gram-positive and Gram-negative bacteria.

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The synthesis, antibacterial activity, and stability to human dehydropeptidase-1 (DHP-1) of a novel series of (5R, 6S)-6-[(1R)-1-hydroxyethyl]-2-heterocyclylcarbapen-2-em-3-carboxylates are described. Of the compounds investigated 1, 5-disubstituted pyrazol-3-yl and 3-substituted isoxazol-5-yl derivatives have the best combination of antibacterial activity and stability to DHP-1. They are particularly active against community-acquired respiratory tract pathogens and have stabilities to DHP-1 superior to that of meropenem.

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