A Gram-negative bacterium produces new monocyclic β-lactam antibiotics with a formylamino substituent, named formadicins A, B, C and D. The producing bacterium was taxonomically characterized and designated as Flexibacter alginoliquefaciens sp. nov. YK-49. Formadicins have narrow antibacterial spectra. They are highly active against some species of Pseudomonas, Proteus and Alcaligenes. Of the four, formadicin C shows the most potent antibacterial activity. Several amino acids such as glycine, D-alanine and D-leucine were antagonistic against formadicins. Formadicins, especially formadicins A and C having the formylamino substituent bound to the 3-position of a β-lactam nucleus, were highly resistant to hydrolysis by various types of β-lactamases. Formadicins A and C showed affinity for penicillin-binding proteins (PBPs) 1A and 1B in Pseudomonas aeruginosa IFO 3080, but formadicin B and nocardicin A showed affinity only for PBP 1B. Formadicins A and C did not lyse Escherichia coli LD-2 solely at their MICs, but when combined with mecillinam each induced a rapid lysis of this organism.

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New monocyclic βbeta;-lactam antibiotics, formadicins A, B, C and D, were isolated from the culture filtrate of Flexibacter alginoliquefaciens sp. nov. YK-49 by various types of column chromatography and preparative reverse-phase HPLC. Their structures were determined by spectroscopic analyses and degradation studies. They have a nocardicin-type skeleton and a formylamino group at the 3- or 12-position. Formadicins A and B each have a D-glucuronide moiety and give formadicins C and D, respectively, upon hydrolysis using βbeta;-D-glucuronidase.

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New 7-methoxycephem antibiotics were found in culture filtrates of a bacterium isolated from a plant and named cephabacin M_1-6. They are the first members of 7-methoxycephem antibiotics of bacterial origin. The producing organism was taxonomically characterized and identified as Xanthomonas lactamgena YK-431; other strains of this species have recently been reported to produce cephabacin F and H group antibiotics. Cephabacin M_1-6 exhibited moderate antibacterial activity against Gram-negative and Gram-positive bacteria. Cephabacin M_1-6 were as stable as cephamycin C to cephalosporinases. They showed inhibitory activity against a cephalosporinase of Proteus vulgaris GN 4413. The mode of action of cephabacin M, was examined using Escherichia coli and Bacillus subtilis as test organisms; primary lethal targets of cephabacin M₁ are penicillin-binding protein (PBP) 1 in E. coli and PBP 4 in B. subtilis.

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Six components of new cephem antibiotics, cephabacin M_1-6, were isolated from the culture filtrate ofXanthomonas lactamgena YK-431 by various types of column chromatographies and preparative reverse-phase HPLC. Their structures were determined by spectroscopic analyses and degradation studies. They consist of 7-methoxydeacetylcephalosporin C as a nucleus and a tri- to heptapeptide including a new amino acid, which is bound at the 3-position with an ester bond.

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Glycocinnasperimicin D was isolated from the fermentation filtrate of a strain ofNocardia sp. using various procedures of column chromatography. Glycocinnasperimicin D exhibited broad antibacterial spectrum. Its chemical structure was determined by NMR spectrometric analyses.

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From the culture broth ofStreptomyces nodosus MH190-16F3, four new antibiotics have been isolated, and named saquayamycins A, B, C and D. The compounds are glycosides of aquayamycin, and among aquayamycin-group antibiotics they are most closely related to P-1894B (vineomycin A₁). All saquayamycins act on Gram-positive bacteria and inhibit the growth of adriamycin-sensitive and adriamycin-resistant P388 leukemia cells.

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Anti-yeast activity with a series of chryscandin derivatives showed that theO-methyl-Ltyrosyl moiety is not always required for activity at the target site. On the other hand, the adenyl-3'-aminoribofuranuronic acid moiety seems to be essential for biological activity. Therefore, the various acyl derivatives on the amino group of the sugar part of the nucleoside were synthesized. 1-(6-Amino-9H-purin-9-yl)-3-(S-benzyl-L-cysteinylamino)-1, 3-dideoxy-β-D-ribofuranuronic acid (16) showed the highest efficacy among them againstCandida albicans. It exhibited sixteen-fold enhanced activityin vitro compared with that of native chryscandin. Thein vivo activity of16 against experimental infection ofC. albicans showed the almost same as that of 5-fluorocytosine and a superior to that of ketoconazole.

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Increased production of sinefungin, a very potent antifungal and antiparasitic nucleoside antibiotic was achieved by medium and strain improvement. When soybean-meal, dextrin and yeast extract were added as carbon and nitrogen sources to the fermentation medium, instead of corn steep liquor, soya-oil and glucose; the antibiotic yield increased from 40 μg/ml to 126 μg/ml with low biomass production. Strain improvement was attempted by two methods. The mean antibiotic yield of the variants after multistep mutagenesis by N -methyl- N '-nitro- N -nitrosoguanidine and ethyleneimine was 466 μg/ml. Protoplasts of the parental strain were prepared by lysozyme digestion from mycelia grown in a medium containing 0.7% glycine. The mean activity of the regenerated protoplasts was 664 μg/ml. Thus, the overall sinefungin production could be increased 16-fold.

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Extracts ofStreptomyces fradiae 75-078, a producer of an antibiotic neomycin, were found to catalyze three reactions which are included in the proposed biosynthetic pathway to 2-deoxystreptamine; amination of deoxyinosose yielding deoxyinosamine, conversion of deoxyinosamine to 2-deoxystreptamine and deamination of 2-deoxystreptamine. Glutamine was effective as an amino-donor for both transamination reactions; conversions of deoxyinosose to deoxyinosamine and of aminodeoxyinosose to 2-deoxystreptamine. Conversion of deoxyinosamine to 2-deoxystreptamine, presumably including successive dehydrogenation and transamination at position 1, was stimulated by NAD⁺. On DEAE-Sepharose CL-6B ionexchange chromatography, the enzyme activity catalyzing amination of deoxyinosose and deamination of 2-deoxystreptamine was eluted as an entity (aminotransferase), while the one converting deoxyinosamine to 2-deoxystreptamine, only if the aminotransferase is supplemented, can be eluted as a separate peak (deoxyinosamine dehydrogenase). The molecular weight of the aminotransferase was estimated to be 130, 000 daltons by chromatography on Sepharose CL-6B. Enzymatic synthesis of 2-deoxystreptamine from deoxyinosose was demonstrated by the cell free extracts.

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By using a strain ofStreptomyces willmorii, daunorubicin (daunomycin) was stereoselectively Converted intoN-acetyl-13(S)-dihydrodaunomycin and bisanhydro-13-dihydrodaunomycinone. The absolute stereochemistry of the new chiral center inN-acetyl-13(S)-dihydrodaunomycin was established by means of nuclear Overhauser effect measured in the 9, 13-O-isopropylidene derivative.

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Two mutants of the tylosin-producingStreptomyces fradiaedefective in the biosynthesis of the macrolide antibiotic tylosin were isolated from colonies derived from regenerated protoplasts. Both strains were unable to carry out any of at least seven tylosin biosynthetic steps and were sensitive to tylosin. One strain, JS82, was also more sensitive to chloramphenicol (Cm), mitomycin C (Mc), hygromycin B (Hm) and kanamycin (Km) than its parent strain. The other strain, JS87, was also more sensitive to Cm than wild type but expressed normal levels of resistance to Me and Hm. Both strains expressed genetic instabilities associated with auxotrophy or expression of antibiotic resistance. Since the genetic instabilities were not due to defective error-free or error-prone DNA repair, they appear to be due to genetic rearrangements associated with the deletion or amplification of sequences linked to and perhaps encompassing tylosin biosynthesis genes.

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Myxovalargin A has two modes of action. At low concentrations (below 1 μg/ml) it inhibits bacterial protein synthesis specifically and instantaneously. In vitroexperiments suggest that it interferes with the binding of aminoacyl tRNA to the A site of the ribosome. At higher concentrations (above 5 μg/ml), or upon prolonged incubation, the antibiotic damages cell membranes. This leads to secondary effects, like decreased O₂consumption or instant break down of RNA synthesis, and may be the reason for the irreversibility of the antibiotic action. The membrane effect is not restricted to prokaryotes and may explain the high toxicity of the compound for higher organisms.

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An aminoglycoside 3' type III phosphotransferase derived fromStaphylococcus aureus Plasmid pRN1956 was cloned on the high copy number Streptomycetes sectors pIJ702 and pIJ704. Streptomyces lividanstransformants carrying the hybrid plasmids show a resistance pattern towards aminoglycoside antibiotics comparable to the resistance pattern ofS. aureus. The APH(3')-III with expanded spectrum of resistance, is a useful additional marker for gene cloning in Streptomycetes.

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Rabbit antisera highly specific to the bleomycinic acid moiety of bleomycins were obtained by immunizing with a conjugate of copper-complex of bleomycin A₅and bovine serum albumin. These antisera not only reacted with bleomycin A₅but also with other bleomycins such as bleomycin A₂, bleomycin B₂and peplomycin. The antisera showed little cross-reactivity with deamido-, depyruvamido- and decarbamoyl-bleomycins. Thus, these antisera were found to be highly specific for the intact bleomycinic acid moiety. One of the antisera was successfully applied to radioimmunoassay of bleomycin and peplomycin in mouse and human sera. The detection limit was 1 ng/ml. This radioimmunoassay is expected to be widely used for the determination of active bleomycins in biological and clinical samples.

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Chinese hamster lung cell line V79 wasca. 13 times more resistant to peplomycin (PEP), and 6 times more resistant to bleomycin (BLM)-A₂than Chinese hamster ovary (CHO) cell line. The natural resistance of V79 cells to PEP or BLM was attributed to higher levels of BLM hydrolase activity and lower cellular uptake of the antibiotic. The sensitivity to PEP of a mutant clone CHO/O-2 T-1 was similar to that of CHO. A hybrid clone of CHO/O-2 T-1 × V79 showed an intermediate sensitivity to PEP between those of both parental cell lines, suggesting that the gene responsible for the natural resistance to PEP appears codominantly in the hybrid. The BLM hydrolase activity of the hybrid was also found intermediate between those of both parental cells. Mutant clones CHO/O-2 T-5 and CHO/O-2 T-6 were 8.3-9.0 times more sensitive to PEP than CHO cells. Hybrid clones CHO/O-2 T-5×V79 and CHO/O-2 T-6×V79 displayed PEP sensitivity similar to that of V79, suggesting that the gene responsible for the PEP supersensitivity (PEP^SS) behaves recessively in the hybrids. Both PEP^SSclones showed levels of BLM hydrolase and cellular uptake of [³H]PEP similar to the parental CHO cells, suggesting that the PEP^SSis due to neither BLM hydrolase nor cellular uptake of the antibiotic. Increased PEP-induced DNA cleavage and decreased DNA repair in the PEP^SSclones were demonstrated by alkaline sucrose density gradient sedimentation method. The results suggest that the PEP^SSof these mutant clones is attributed to decreased DNA-repairing activity and/or increased DNA-breaking activity.

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