SUMMARY: Production of the volatile metabolite, isobutyraldoxime -methyl ether (IBME) by a -like organism NCIB 11650 was investigated under a variety of environmental conditions using gas chromatography. Under aerobic conditions up to 10 μg IBME ml was produced on mineral salts media containing 0.5% (w/v) glucose or succinate as sole C source with 0.1% (w/v) NHCl as sole N source. Exogenous -valine further stimulated IBME formation up to 25 μg ml but supplementation of the medium with -isomer or other amino acids had little effect on IBME production and did not lead to the appearance of analogues of IBME. Trapping experiments using [C]valine confirmed that IBME was derived from this amino acid. Several other bacterial species examined, e.g. sp. NCIB 11652, another -like organism NCIB 11651 and sp. NCIB 11653 also produced IBME under similar conditions. The strain synthesized up to 20 μg ml in the absence of valine and up to 90 μg ml in its presence.

The production of IBME exhibited many features characteristic of the formation of a secondary metabolite. Thus biosynthesis was confined to a narrower range of temperature than cell division, was almost completely suppressed by 300 mM-phosphate and was inhibited by high concentrations of readily utilizable C sources. Although IBME synthesis in the -like organism NCIB 11650 appeared to be growth-related, its formation by both the sp. and the -like organism NCIB 11651 was delayed until the late-exponential and early-stationary phases of growth. The biological significance of this novel class of secondary metabolite is discussed and a possible biosynthetic route proposed.


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