ISOLATION OF ACTINOMYCES-VISCOSUS STRAIN GA - CHARACTERISTICS OF ITS CELLULAR BIOLOGICAL RETARDANT(S)

Actinomyces viscosus strain GA produces an exocellular biological reta rdant(s) that prevents certain vegetable plants from becoming overgrow n. The biological retardant(s) was assayed using the etiolated wheat c oleoptile assay, and fractionation of culture supernatant fluid result ed in a partial purification of the retardant(s). The biological retar dant(s) was most active around pH 7 in the bioassay and when applied t o sterile soil mixture. The biological retardant(s) was tentatively id entified as a derivative of a rare hexose carbohydrate (but not an ami no sugar) but an exact structure was not determined. In a sterilized s ynthetic soil system, the biological retardant(s) has an effect on tom ato cultivars similar to that observed by the synthetic plant growth r egulators Alar (succinic acid 2,2-dimethylhydrazide) and Bonzi (paclob utrazol).