The aminoglycoside phosphotransferase of Pseudomonas aeruginosa 21-75 was purified by affinity chromatography using dibekacin-Sepharose 4B or lividomycin A-Sepharose 4B followed by DEAE Sephadex A-50 chromatography. It had activities of both the known aminoglycoside 3'-phosphotransferases I and II, and transferred phosphate from ATP to the 3'-hydroxyl group of kanamycin A, ribostamycin and butirosin A and 5"-hydroxyl group of lividomycin A. This enzyme was designated aminoglycoside 3'-phosphotransferase III. It showed strong substrate inhibition by kanamycin A and ribostamycin when their concentration exceeded 6μM. Purification and characterization of this enzyme are reported.

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Septamycin is a metal complexing polyether antibiotic produced by a strain of Streptomyces hygroscopicus NRRL 5678. The metabolite, a monocarboxylic acid, was isolated as the sodium salt C₄₈H₈₁NaO₁₆. The crystal structure and absolute configuration were established by X-ray analysis of the p-bromophenacyl derivative. Septamycin has a thirty-carbon backbone and contains seven heterocyclic rings. Supported by direct comparison septamycin proved to be identical with antibiotic A28695 A isolated from Streptomyces albus NRRL 3883. The metabolite is active against gram-positive

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Nanaomycins are new antibiotics produced by the strain OS-3966 which was designated Streptomyces rosa var. notoensis. Nanaomycins A and B were isolated from the culture filtrate by extraction with organic solvent and silica gel chromatography. The physical and chemical properties suggest that nanaomycins A and B are quinone-related compounds having the molecular formulae, C₁₆H₁₄O₆ and C₁₆H₁₆O₇, respectively. Nanaomycins A and B inhibit mainly mycoplasmas, fungi and Gram-positive bacteria. The acute toxicities (LD₅₀. ip) of nanaomycins A and B in mice are 28.2 and 169 mg/kg, respectively.

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Evidence is put forward which describes the structure and stereochemistry of new antibiotics, nanaomycins A and B, as I and V, respectively. In order to study biosynthesis and to determine the position of the hydroxyl group in the naphthoquinone moiety, a feeding experiment with 1-¹³C-acetate was effectively carried out. Nanaomycins
A and B were found to be synthesized from acetate via a polyketide by Streptomyces rosa var. notoensis.

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Pyridindolol is a product of a streptomyces and exhibits inhibitory activity against bovine liver β-galactosidase. The structure of pyridindolol, 1-[1(R), 2-dihydroxyethyl]- 3-hydroxymethyl-⁹H-pyrido[3, 4-b] indole, has been established by spectroscopic analyses and an X-ray structure determination. Pyridindolol (I) inhibits bovine liver β-galactosidase in acidic conditions and its production, isolation and properties were reported in a previous paper1). This paper is concerned with the structure determination of the new inhibitor.

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A mutant with enhanced potential to utilize sulfate for cephalosporin C production was isolated from a strain of Cephalosporium acremonium. The mutant displayed potency levels more than twofold that of the parent in the presence of sulfate but its productivity was severely inhibited by more than 0.5 % of methionine which gave high cephalosporin C production with the parent. In a complex medium norleucine stimulated cephalosporin C production by the mutant in the presence of sulfate, whereas it showed no effect on the parent. In an incubation system with sulfur-starved cells of the mutant, L-methionine, but not the D-isomer, gave lower cephalosporin C production and a delayed production of penicillin N. However, it exhibited a stimulatory effect in the presence of valine or α-aminoadipic acid, the constituent amino acids of the antibiotic. Norleucine showed a similar effect to that of L-methionine in the presence of sulfate. On the basis of these results, characteristics of the mutant are discussed in connection with the effect of methionine.

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The previously reported¹²⁾ inability of methionine to stimulate cephalosporin C production in a cysteine auxotroph is due to cysteine interference with methionine uptake. In such a case, "illicit transport" of alanylmethionine can be used to demonstrate the efficacy of methionine in such mutants blocked in the path from methionine to cysteine. This result supports the hypothesis that the stimulatory activity of methionine is not due to its ability to donate sulfur to the cephalosporin C molecule.

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The chemically modified polyene macrolide antibiotic, amphotericin B methyl ester (AME), exhibited a concentration-dependent growth stimulatory effect on established lines of mouse (L-M) and monkey (Vero) cells. Stimulation was indicated by increases in growth rate, and in the enhanced synthesis of DNA and RNA. In contrast, the parental antibiotic amphotericin B and the desoxycholate complex of amphotericin B, Fungizone R, did not elicit a similar proliferative response in L-M or Vero cells. AME was not growth-promoting toward low passage strains of mouse(PMK 6) and monkey cells (GMK 8).

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The binding of kasugamycin to the E. coli ribosomes has been demonstrated by equilibrium dialysis. Kasugamycin binds to the 70S ribosomes in a molar ratio of 1:1. The association constant is approximately 6×10⁴ M^-1. The antibiotic binds to the 30S subunit as well as to 70S ribosomes, but only slightly to the 50S subunit. The binding of kasugamycin is not significantly affected by the presence of other aminoglycoside antibiotics: streptomycin, kanamycin. or gentamicin. Kasugamycin does not bind to ribosomes derived from a kasugamycin-resistant mutant, ksgC.

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The characteristics of spontaneous fosfomycin-resistant cells isolated in vitro were investigated. Distribution of resistance level to the drug in Escherichia coli B was thought to be broad and, for this reason, resistance to the drug seemed to develope easily in vitro.In the process of isolating the resistant cells, two groups of cells, differing in colony size, were distinguished. Smaller colony-forming cells appeared more frequently than Larger colony-forming ones. Many of the former seemed to be slow growers and decreased simultaneously in utilization of several carbohydrates. One of the Smaller colony-forming isolates was distinctly different from glp T^- or uhp^-.

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α-Carboxy-3-thienyhnethyl penicillin (ticarcillin) is a relatively new semisynthetic penicillin which is more active than carbenillin against Pseudomonas aeruginosa. Among the strains tested, those isolated from the respiratory tract showed an increased susceptibility to carbenicillin and ticarcillin. As with carbenicillin, synergistic activity against P. aeruginosa could be demonstrated with ticarcillin in combination with gentamicin. Like other penicillins, the antibacterial activity was influenced by the inoculum size. The antibacterial activity of ticarcillin showed the compound to be almost equally active with carbenicillin and ampicillin against Escherichia coli and Klebsiella aerogenes, but less active than carbenicillin and ampicillin against indole-negative Proteus strains. Regarding the indole-positive Proteus species, at relatively low antibiotic concentrations the proportion of strains sensitive to ticarcillin was greater than to carbenicillin or ampicillin whereas at relatively high antibiotic concentrations the converse was the case. It is interesting to note that a high proportion of strains of E. coli and K. aerogenes were resistant to the three penicillins even at a concentration of 200μg/ml, while 70% of Proteus strains were inhibited by these drugs at the same concentration. Disc susceptibility tests with ticarcillin were carried out according to BAUER-KIRBY method³⁾.

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