Actinomycin formation by Streptomyces cultures

Genetic interrelations in the actinomycin biosynthetic gene clusters of Streptomyces antibioticus IMRU 3720 and Streptomyces chrysomallus ATCC11523, producers of actinomycin X and actinomycin C

Sequencing the actinomycin (acm) biosynthetic gene cluster of Streptomyces antibioticus IMRU 3720, which produces actinomycin X (Acm X), revealed 20 genes organized into a highly similar framework as in the bi-armed acm C biosynthetic gene cluster of Streptomyces chrysomallus but without an attached additional extra arm of orthologues as in the latter. Curiously, the extra arm of the S. chrysomallus gene cluster turned out to perfectly match the single arm of the S. antibioticus gene cluster in the same order of orthologues including the the presence of two pseudogenes, scacmM and scacmN, encoding a cytochrome P450 and its ferredoxin, respectively. Orthologues of the latter genes were both missing in the principal arm of the S. chrysomallus acm C gene cluster. All orthologues of the extra arm showed a G +C-contents different from that of their counterparts in the principal arm. Moreover, the similarities of translation products from the extra arm were all higher to the corresponding translation products of orthologue genes from the S. antibioticus acm X gene cluster than to those encoded by the principal arm of their own gene cluster. This suggests that the duplicated structure of the S. chrysomallus acm C biosynthetic gene cluster evolved from previous fusion between two one-armed acm gene clusters each from a different genetic background. However, while scacmM and scacmN in the extra arm of the S. chrysomallus acm C gene cluster are mutated and therefore are non-functional, their orthologues saacmM and saacmN in the S. antibioticus acm C gene cluster show no defects seemingly encoding active enzymes with functions specific for Acm X biosynthesis. Both acm biosynthetic gene clusters lack a kynurenine-3-monooxygenase gene necessary for biosynthesis of 3-hydroxy-4-methylanthranilic acid, the building block of the Acm chromophore, which suggests participation of a genome-encoded relevant monooxygenase during Acm biosynthesis in both S. chrysomallus and S. antibioticus.

In situ detection of antibiotic amphotericin B produced in Streptomyces nodosus using Raman microspectroscopy

The study of spatial distribution of secondary metabolites within microbial cells facilitates the screening of candidate strains from marine environments for functional metabolites and allows for the subsequent assessment of the production of metabolites, such as antibiotics. This paper demonstrates the first application of Raman microspectroscopy for in situ detection of the antifungal antibiotic amphotericin B (AmB) produced by actinomycetes—Streptomyces nodosus. Raman spectra measured from hyphae of S. nodosus show the specific Raman bands, caused by resonance enhancement, corresponding to the polyene chain of AmB. In addition, Raman microspectroscopy enabled us to monitor the time-dependent change of AmB production corresponding to the growth of mycelia. The Raman images of S. nodosus reveal the heterogeneous distribution of AmB within the mycelia and individual hyphae. Moreover, the molecular association state of AmB in the mycelia was directly identified by observed Raman spectral shifts. These findings suggest that Raman microspectroscopy could be used for in situ monitoring of antibiotic production directly in marine microorganisms with a method that is non-destructive and does not require labeling.

Role of valine and isoleucine as regulators of actinomycin peptide formation by Streptomyces chrysomallus

Katz, Edward (Rutgers, The State University, New Brunswick, N. J.), Clarence R. Waldron, and Mary Lou Meloni. Role of valine and isoleucine as regulators of actinomycin peptide formation by Streptomyces chrysomallus. J. Bacteriol. 82:600-608. 1961-d-Valine is an effective inhibitor of actinomycin synthesis by Streptomyces chrysomallus; l-valine stimulates actinomycin production and reverses the inhibition due to the d-enantiomorph. The incorporation of l-valine into the medium results, particularly, in a marked increase in actinomycin IV formation. In studies with various isoleucine isomers it was shown that l-isoleucine enhances actinomycin VII production; the principal effect of d-alloisoleucine and, especially, d-isoleucine, is to bring about synthesis of two new actinomycins which contain N-methylisoleucine. Both l- and d-threonine were observed to have an effect similar to that obtained with l-isoleucine. An interpretation of these findings has been discussed.

Effect of pipecolic acid isomers on the biogenesis of actinomycins

Streptomyces antibioticus produces a family of actinomycin components which differ solely at the "imino acid" site of the molecule; however, new congeners of actinomycin are synthesized when cultures are supplemented with pipecolic acid (PA). The quantitative and qualitative nature of the actinomycins produced differed when cultures were incubated in the presence of either l-, d-, or racemic PA. In the presence of d-PA, the quantitative and qualitative nature of those actinomycins produced were similar to those produced in the absence of supplementation. By contrast, in the presence of l-PA or dl-PA new actinomycin components containing PA were synthesized at the expense of normally produced components. Also, the total amount of antibiotic produced decreased in response to increasing concentrations of exogenously supplied l-PA. This effect occurred whether or not d-PA was also added to cultures. Concentrations of l-PA greater than 125 mug/ml of medium resulted in no additional decrease in the amount of antibiotic produced. Although PA-containing actinomycins were formed as early as 6 h after the addition of 250 mug of l-PA per ml, it was not until 24 h postaddition that the relative percentages of actinomycin components produced approached a constant value. Evidence presented here indicated that the l-isomer of PA replaces l-proline in the pentapeptide of actinomycin.

Phenoxazinone synthetase from Streptomyces antibioticus: multiple activities of the enzyme

A procedure for the preparation of relatively large quantities of highly purified phenoxazinone synthetase from Streptomyces antibioticus is described. Enzyme preparations consisted of multiple forms, as determined by polyacrylamide gel electrophoresis. Each of the electrophoretically separable forms catalyzed the oxidation of catechols, ferrocyanide, and ethylenic thiols, in addition to o-aminophenols.

Biosynthesis of the actinomycin chromophore: incorporation of 3-hydroxy-4-methylanthranilic acid into actinomycins by Streptomyces antibioticus

Actinomycin synthesis by washed mycelia of Streptomyces antibioticus has been conducted in the presence of 3-hydroxy-4-methylanthranilate-(carboxyl-(14)C). Incorporation of this compound into actinomycins has been observed, which constitutes further evidence that 3-hydroxy-4-methylanthranilate is an intermediate in actinomycin biosynthesis. The position of the incorporated label has been determined to be within the actinomycin chromophore, and the label appears to be equally distributed between both halves of the chromophore. Incidental to these findings was the observation that the (14)C-labeled actinomycins were subject to rapid reabsorption by the organism with actinomycin V taken up preferentially to actinomycin IV.

Origin of the sarcosine molecules of actinomycins

1. Streptomyces V-187 produces on minimal medium a mixture composed mainly of actinomycin C(1) (actinomycin D) and actinomycin A(1) (actinomycin I). If sarcosine is added to the medium, the micro-organism produces, in addition to actinomycins C(1) and A(1), actinomycin F(8) (actinomycin II) and actinomycin F(9) (actinomycin (III), characterized by the substitution by sarcosine of one or both the proline molecules present in actinomycin C(1). 2. Exogenous sarcosine seems to be incorporated as such by Streptomyces V-187 only in the sarcosine molecule(s) that replace proline in the actinomycins of the F group, whereas, for the synthesis of the other sarcosine molecules, the amino acid is first demethylated to glycine. 3. The incorporation of sarcosine and glycine into actinomycin by Streptomyces antibioticus appears to follow a similar pattern, except that a portion of the methyl group produced in the degradation of sarcosine is utilized as a source of the methyl groups of the antibiotic. This explains the previously reported lack of cross-dilution between glycine and sarcosine observed in the incorporation of these amino acids into actinomycin.