Actinomycete metabolism: origin of the guanidine groups in streptomycin

Radioactive Myoinositol: Incorporation into Streptomycin

Radioactive myoinositol was rapidly incorporated into streptomycin by Streptomyces griseus. All the incorporated radioactivity was found in the streptidine moiety of the antibiotic, as shown by chemical degradation of the streptomycin. To a certain extent inositol reversed the depressing effect of phosphate on the production of the antibiotic.

Variations in Strains of Streptomyces griseus Isolated from a Degenerating Streptomycin-Producing Culture

Streptomycin-resistant strains were isolated from a degenerated streptomycin-producing culture of Streptomyces griseus. From 250 resistant strains, 3 low, 2 intermediate, and 2 high potency strains were selected; these were compared in their morphological, cultural, physiological, and streptomycin-producing properties. Though no definite correlation between streptomycin production and the other properties could be obtained, the following correlations were considered as distinct differences among the low, intermediate, and high potency strains. (i) When streptomycin-producing ability degenerates, more submerged spore formation or fragmentation of mycelium into shorter filaments appears to occur. (ii) On agar medium, low and intermediate potency strains often show finely wrinkled growth; high potency strains do not show such characteristics. (iii) High potency strains excrete a distinct yellow soluble pigment on synthetic agar medium and on glucose-yeast extract agar, but low and intermediate potency strains show little or no ability to form this soluble pigment. (iv) In low and intermediate potency strains, inositol and arginine did not stimulate streptomycin production as they did in high potency strains. Streptamine showed some stimulating effect in the high potency strains and, in contrast, a depressive effect in intermediate potency strains, though streptidine showed a distinctly stimulating effect in all groups of strains employed.

Secondary metabolite biosynthesis: the first century

An account of work on the biosynthesis of secondary metabolites up to 1965 is presented. The earliest suggestions for three of the four major pathways were speculative; for the isoprene rule, hypotheses date to 1877, for the polyketide rule to 1907, and for a role for amino acids in alkaloid biosynthesis to 1910. The fourth major pathway based on intermediates of the shikimic acid pathway has a much shorter history because shikimic acid itself was only identified as a primary metabolite in 1951. In addition to speculation, biomimetic syntheses were carried out in which chemists attempted to duplicate possible biosynthetic pathways in vitro. The classic example was Robinson's synthesis of tropinone in 1917. Direct examination of secondary metabolite biosynthesis was possible with the use of the isotopic tracer technique. This methodology, applied extensively to primary metabolism beginning in 1935 and to secondary metabolism from about 1950, was facilitated by the increasing availability of the 14C isotope. With the use of isotopes as tracers, the broad outlines of secondary metabolite biosynthesis, reviewed here, were established in the period 1950 to 1965.

Studies on the biosynthesis of streptomycin

Myo-inositol, especially in combination with arginine, enhances streptomycin production. Compounds which show structural relationship with myo-inositol are ineffective.Myo-inositol decreases the incorporation of C(14)-glucose into streptomycin, particularly into streptidine. This effect suggests that myo-inositol is a precursor of the streptidine ring. Methionine stimulates antibiotic production in a synthetic medium but proves to be unfavorable in a complex medium. The gamma- and delta-isomers of hexachlorocyclohexane inhibit streptomycin formation. The formation of streptomycin by washed mycelium was studied. Essentially the same results were here obtained as with growing cultures.

Myo-inositol in the biosynthesis of streptomycin by Streptomyces griseus

When myo-inositol is present in a growing culture of Streptomyces griseus the yield of streptomycin is increased, and the amount of carbon-14-from uniformly labeled glucose-incorporated into the streptidine and streptobiosamine moieties of streptomycin is lowered by 41 percent and 21.7 percent, respectively. These results present strong indirect evidence for the participation of myo-inositol or its metabolic products in streptidine biosynthesis.

Production of volatile nitrogenous compounds from the degradation of streptomycin by Pseudomonas maltophilia

Ammonia, methylamine, and pyridine were detected in broth filtrates of a streptomycin-degrading strain of Pseudomonas maltophilia during growth on streptomycin as a sole carbon and nitrogen source. Ammonia and methylamine, quantitatively measured by conversion to chromophores with picryl sulfonic acid, were found to accumulate in broth, whereas pyridine concentration increased in the early stages of streptomycin degradation and then decreased as the degradation of the antibiotic neared completion. Exogenous pyridine was metabolized by washed-cell suspensions. Use of N-streptomycin-methyl-(14)C showed that the methylamine arose from the N-l-glucosamine-methyl moiety of streptomycin. Methylamine was an end product and was not further metabolized by cells.