Biosynthesis of monobactam compounds: origin of the carbon atoms in the beta-lactam ring.

The biosynthesis of monobactams by strains of Chromobacterium violaceum, Acetobacter sp., and Agrobacterium radiobacter was studied. Monobactams were produced during logarithmic growth by C. violaceum and Acetobacter sp. and during late log growth on glycerol and in stationary phase by A. radiobacter. The addition of various amino acids failed to significantly stimulate monobactam production in any of the producing organisms. Several 14C-amino acids and pyruvate were incorporated in vivo into monobactams. Serine, glycine, and cysteine were better incorporated than alanine or aspartate, whereas an excess of nonradioactive serine depressed the incorporation of labelled cysteine, glycine, and pyruvate. A comparison of [1-14C] glycine and [2-14C] glycine incorporation data suggests that glycine was first converted to serine. With a mixture of [U-14C[serine and [3-3H]serine, C. violaceum synthesized a monobactam with a complete retention of tritium, whereas with a [U-14C] cystine and [3-3H] cystine mixture, there was an extensive loss of C-3 tritium. Acetobacter sp. and A. radiobacter also utilized the double-labeled serine without the loss of tritium in their respective monobactams. It appears, therefore that in the three organisms, the carbon atoms of the beta-lactam ring of the monobactam are derived directly from serine without the loss of the C-3 hydrogen atoms, probably by an SN2 ring closure mechanism. With [methyl-14C] methionine, most of the radioactivity in the monobactam from Acetobacter sp. was in the methyl moiety of the beta-lactam ring methoxyl group.

Epithienamycins-novel beta-lactams related to thienamycin. I. Production and antibacterial activity.

The epithienamycins are cell wall active antibiotics structurally related to N-acetylthienamycin. We have found forty-three isolated of Streptomyces flavogriseus which are capable of producing members of the epithienamycin family. Six major epithienamycin components, and xanthomycin, have been isolated from fermentation broth. Fermentation conditions can be varied to enrich for certain members of the epithienamycin family. All six components show activity in vitro versus a broad spectrum of bacterial species. The weight potencies vary 27 fold from the most active to least active.

PS-6 and PS-7, new beta-lactam antibiotics. Isolation, physicochemical properties and structures.

Antibiotics PS-6 and PS-7 which are shown to be 5R,6R-3-(2-acetamido)ethylthio-6-isopropyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene- 2-carboxylic acid and 5R,6R-3-(E)-(2-acetamido) vinylthio-6-ethyl-7-oxo-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid respectively, are new beta-lactam compounds isolated from fermentation broths of Streptomyces cremeus subsp. auratilis A271, S. fulvoviridis A933, S. olivaceus ATCC 31126 and S. flavogriseus NRRL 8139. Fermentation, isolation, physicochemical properties and structures of antibiotics PS-6 and PS-7 are described.

Four further antibiotics related to olivanic acid produced by Streptomyces olivaceus: fermentation, isolation, characterisation and biosynthetic studies.

Four beta-lactam antibiotics with beta-lactamase inhibitory activity MM 22380, MM 22381, MM 22382 and MM 22383 containing the carbapenem nucleus have been isolated from a culture of Streptomyces olivaceus ATCC 31365. Fermentation conditions for their production and methods for their isolation are described. Evidence for a biosynthetic link between these compounds and the previously described olivanic acid derivatives MM 4550, MM 13902 and MM 17880 is presented.

PS-5, a new beta-lactam antibiotic. I. Taxonomy of the producing organism, isolation and physico-chemical properties.

Antibiotic PS-5 is a new beta-lactam antibiotic isolated from fermentation broths of Streptomyces sp. strain A271. The strain was considered to be a new subspecies of Streptomyces cremeus and the name, Streptomyces cremeus subsp. auratilis, was proposed. Fermentative production, isolation and physico-chemical properties of PS-5 are described.

Olivanic acids, a family of beta-lactam antibiotics with beta-lactamase inhibitory properties produced by Streptomyces species. II. Isolation and characterisation of the olivanic acids MM 4550, MM 13902 and MM 17880 from Streptomyces olivaceus.

The olivanic acids MM 4550, MM 13902 and MM 17880 are members of a new family of beta-lactam antibiotics. An isolation and purification process utilising ion-par extraction and ion-exchange chromatography is described and the metabolites are characterised by physico-chemical and biological properties.

Olivanic acids, a family of beta-lactam antibiotics with beta-lactamase inhibitory properties produced by Streptomyces species. I. Detection, properties and fermentation studies.

The screening of soil actinomyces for beta-lactamase inhibitors is described. Using a plate test a number of strains of Streptomyces were found to produce beta-lactamase inhibitory activity designated olivanic acid complex. Factors affecting the production of this complex by Streptomyces olivaceus ATCC 21379 are reported. The complex showed antibacterial activity and also inhibited a number of different types of beta-lactamase in a progressive manner. Certain ampicillin-resistant bacteria are rendered sensitive to ampicillin in the presence of olivanic acid complex at a concentration which alone did not inhibit growth.

Thienamycin, a new beta-lactam antibiotic. I. Discovery, taxonomy, isolation and physical properties.

A new beta-lactam antibiotic, named thienamycin, was discovered in culture broths of Streptomyces MA4297. The producing organism, subsequently determined to be a hitherto unrecognized species, is designated Streptomyces cattleya (NRRL 8057). The antibiotic was isolated by adsorption on Dowex 50, passage through Dowex 1, further chromatography on Dowex 50 and Bio-Gel P2, and final purification and desalting on XAD-2. Thienamycin is zwitterionic, has the elemental composition C11H16N2O4S (M.W. = 272.18) and possesses a distinctive UV absorption (lambda max = 297 nm, epsilon = 7,900). Its beta-lactam is unusually sensitive to hydrolysis above pH8 and to reaction with nucleophiles such as hydroxylamine, cysteine and, to a lesser degree, the primary amine of the antibiotic itself. The latter reaction results in accelerated inactivation at high antibiotic concentrations.

Studies on the biosynthesis of clavulanic acid. I. Incorporation of 13C-labelled precursors.

The biosynthesis of clavulanic acid was investigated by feeding 13C-labelled precursors to Streptomyces clavuligerus fermentations. The resulting samples of clavulanic acid were isolated as the benzyl ester and were examined by 13C NMR spectroscopy for 13C-enrichment. The results showed that the carbon skeleton of 1,3-13C2-glycerol was incorporated intact into the three beta-lactam carbons of clavulanic acid. Studies with 1-13C-acetate, 2-13C-acetate and 1,2-13C2-acetate indicated that the remaining five carbons of clavulanic acid were probably derived from alpha-ketoglutarate. 1-13C-Propionate and 3-13C-propionate were not metabolised via the same route as glycerol, but were probably converted to succinate, via methylmalonyl CoA, and hence via the tricarboxylic acid cycle to the clavulanic acid precursors.

Nocardicin A, a new monocyclic beta-lactam antibiotic. I. Discovery, isolation and characterization.

Nocardicin A is a new monocyclic beta-lactam antibiotic obtained from the fermentation broth of a strain of actinomycetes. The producing organism, strain WS 1571, was identified as Nocardia uniformis subsp. tsuyamanensis ATCC 21806. The antibiotic, obtained as colorless crystals, exhibits moderate in vitro antibacterial activity against a broad-spectrum of Gram-negative bacteria including Proteus and Pseudomonas. It has low toxicity in laboratory animals.