Incorporation of sarcosine into the actinomycins synthesized by Streptomyces antibioticus

Carbon-14-glyphosate behavior in relationship to pedoclimatic conditions and crop sequence

The recognition of glyphosate [(-phosphonomethyl) glycine] behavioral patterns can be readily examined using a pedoclimatic gradient. In the present study, glyphosate adsorption-desorption and degradation were examined under different scenarios in relationship to soil properties and soil use applications. Three sites with varied pedoclimatic conditions and two crop sequences were selected. Adsorption-desorption and glyphosate distribution in mineralized, extractable, and nonextractable fractions were assessed under laboratory conditions. Glyphosate sorption was characterized by isotherms and glyphosate degradation using the distribution of C-glyphosate radioactivity among mineralized fractions, two extractable fractions (in water, ER1; in NHOH, ER2), and nonextractable fractions. Results showed sorption indices (distribution coefficient and Freundlich sorption coefficient : 13.4 ± 0.3-64.1 ± 0.9 L kg and 16.2-60.6, respectively), and hysteresis increased among soil sites associated with decreasing soil particle size <2 μm, soil organic matter, and other soil properties associated with soil granulometry. A multiple stepwise regression analysis was applied to estimate the relationship between values and soil properties. Cation exchange capacity, water field capacity, and Bray-1 P were the soil properties retained in the equation. Soils under continuous soybean [ (L.) Merr.] (monoculture) treatment exhibited reduced glyphosate adsorption and decreased hysteresis desorption relative to soils under rotation. To our knowledge, these results are the first to demonstrate that soils with identical properties exhibited different glyphosate retention capacities based on crop sequence. We propose possible explanations for this observation. Our results suggested that characterization of the variability in soil property gradients can serve to determine glyphosate behavioral patterns, which can establish a criterion for use in reducing potential environmental risks.

Actinomycin biosynthesis by protoplasts derived from Streptomyces parvulus

Conditions are described for the formation of protoplasts from Streptomyces parvulus that are able to synthesize actinomycin D de novo. Antibiotic synthesis by protoplasts, in contrast to that by mycelium, was sensitive to inhibition by actinomycin D and to a decrease in sucrose concentration. On the other hand, synthesis by mycelium was much more sensitive to inhibition by amino acid analogs (d-valine, cis-3-methylproline, and alpha-methyl-dl-tryptophan). In addition, the uptake of amino acids (l-methionine, sarcosine, and l- and d-valine) by protoplasts was significantly lower than that by mycelium. The advantages and limitations of using protoplasts for studying in vivo actinomycin synthesis are discussed.

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.