Isolation and structures of nitrogen-free platenolide glycosides. I. The 5-O-(deoxy-3'-C-acetyl-beta-D-hexopyranosyl)-platenolides I and II

Production of a novel polyketide through the construction of a hybrid polyketide synthase

The lactone rings of the polyketides platenolide and tylactone are synthesized by condensation of acetate-, proprionate-, and butyrate-derived precursors. A hybrid tylactone/platenolide synthase was constructed to determine if the choice of substrate is programmed by the polyketide synthase and to ascertain if a substrate different than that normally used in the first step of platenolide synthesis could be incorporated into the final polyketide. In this work, we report the successful incorporation of a propionate in place of the acetate normally used in the first step of platenolide synthesis. This result demonstrates that polyketide synthases choose a particular substrate at defined steps and provides strong evidence that substrate choice is programmed by the acyl transferase domain of a large, multifunctional polyketide synthase.

Bioconversions of a macrolide glycoside by growing L-form cells of Streptomyces hygroscopicus

Growing L-form cells of Streptomyces hygroscopicus were shown to carry out 3-0-acylation and 14-C-hydroxylation of a macrolide glycoside suggesting that both types of bioconversion do neither require the intact cell wall nor the periplasmic space.

[Possibilities for direct manipulation of gene expression of microbial secondary metabolism]

The present review deals with some theoretical and applied aspects of directed manipulations of control mechanisms governing the expression of microbial secondary metabolism. In attempting to make broad generalizations, the production of secondary metabolites is discussed in terms of the cellular differentiation of relevant organisms. On the basis of the actual information about the regulation of microbial idiolite synthesis, some potential ways for the quantitative and the qualitative improvement of secondary metabolite production are discussed. A number of examples demonstrate the effectiveness of rational strategies of strain development, e. g., the removal of non-specific repressions of secondary metabolism by environmental factors, the excessive production of precursors due to altered control of intermediary metabolism, the increased resistance of producer organism against the autotoxicity of some idiolites, the deletion of alternative pathways of the primary and secondary metabolism, manipulations concerning the product spectrum, the deletion of feedback mechanisms, and elimination of degradating pathways in the secondary metabolism etc. The scope and limitations of rational strategies of strain improvement by genetic and physiologic manipulations are subjected to final discussion.