A new streptomycete metabolite named arglecin was isolated from the culture filtrates of the strains KA57-AG3, KB59-M1 and the other 11 strains by the screening of compounds with positive Wood and diacetyl reactions. Thestructure was determined as 5-amino-2-(3-guanidinopropyl)-3, 4-dihydro- 4-isopropylpyridin-3-one.
Cladosporin is a new fungal metabolite produced in good yield in the mycelium of Cladosporium cladosporioid s (Fres.) de Vries. Its structure was established as 3, 4-dihydro-6, 8-dihydroxy-3-(tetrahydro-6-methyl-2H-pyra -2- yl)methylisocoumarin on the basis of spectroscopic studies of the parent compound, mono-and di-methyl derivatives, and a monoacetate. Both cladosporin and monoacetyl cladosporin completely inhibited growth of severa dermatophytes on agar medium at a concentration of 75 μg/ml. The germination of spores from several Fenicillium and Aspergillus spp. was inhibited by these compounds at concentrations of 40 μg/ml or less in liquid medium.
Five micrograms per milliliter of aristeromycin, a nucleoside antibiotic, completely inhibited the growth of Xanthomonas oryzae at all growing stages. When cells of Xanthomonas oryzae were treated with the antibiotic at the beginning of cultivation and transferred to a growth medium without antibiotic, the lag phase was prolonged without the change in the length of the log phase. Incubation of Xanthomonas oryzae with the antibiotic, reduces the viable cell count without affecting the optical density of the cell suspension. It was assumed that aristeromycin inhibited the growth of Xanthomonas oryzae by its bacteriocidal action. Ten to a hundred-fold mounts of either of adenosine, adenine, deoxyadenosine and inosine reversed the growth by aristeromycin. Complete reversal of the cell growth was not seen in the presence of these compounds because of their own growth inhibitory activity. Adenosine exhibited the strongest competitive activity with the antibiotic. It was suggested that the antibiotic acted on the metabolic pathway of adenylic acid, adenosine and adenine.
The effect of bleomycin on the infectivity and the molecular integrity of bacteriophage ΦX174 DNA was examined by means of the spheroplast assay and sucrose density gradient centrifugation. Bleomycins caused degradation of the DNA, both in the single and double stranded forms even in the absence of 2-mercaptoethanol or hydrogen peroxide, although the reaction was accelerated by the addition of either of the compounds.All the bleomycin compounds examined, A2, A5 and B2, were effective for the reaction but copper-chelated A2 was not. The reaction was inhibited by the addition of EDTA*.
The preparation of the acetoxymethyl and pivaloyloxymethyl esters of cephaloglycin is described. These esters are well absorbed from the gastrointestinal tract and after the absorption are cleaved enzymatically with the liberation of cephaloglycin. As a result high blood- and tissue-levels of the latter are attained.
A new antibiotic O-2867 inhibiting the growth of Piricularia oryzae, a plant pathogenic fungus of rice, was isolated from a Streptomyces sp. Antibiotic O-2867 is water-soluble, amphoteric and consists of 2 components, O- 2867-α and β. O-2867-α was obtained as an amorphous powder and O-2867-β as colorless needles. Both antibiotics are active against P. oryzaein vitro but are not effective in pot tests using rice plants infected with P. oryzae.
Sterols like cholesterol, ergosterol, ergocalciferol and stigmasterol can antagonize various reactions of the polypeptide antibiotic mycobacillin on sensitive cells of Aspergillus niger, e. g. growth inhibition, agglutination and release of ultraviolet-absorbing compounds from the cells. Among the lipids tested viz. lecithin, sphingomyelin and cephalin, only lecithin is able to antagonize these antifungal reactions of mycobacillin. The growth-inhibiting property of the antibiotic on A. niger is antagonized by intracellular sterols and lipids isolated from the same sensitive organism. The intracellular antagonists have been characterized mainly as cholesterol and lecithin.
The effect of tunicamycin on the synthesis of macromolecules in cultures of chick embryo fibroblasts was investigated by measuring the incorporation of radioactive percursors into acid-insoluble product after infection or mockinfection with Newcastle disease virus (NDV). Tunicamycin had slight or no effect on incorporation of uridine, thymidine and choline. Protein synthesis proceeded to some extent depending on concentrations of tunicamycin. Incorporation of glucosamine and glucose was greatly affected by the antibiotic at low concentrations. Mechanism of action of tunicamycin against NDV multiplication is discussed in relation to membrane synthesis.