Humic Acid Vitamin Research Articles

Selective isolation of Actinoplanes and Dactylosporangium from soil by using γ-collidine as the chemoattractant

Zoospores of the actinoplanetes Actinoplanes missouriensis and Dactylosporangium thailandense were attracted to a number of amino acids, aromatic compounds and sugars. Among these compounds, d-xylose and γ-collidine served as universal chemoattractants for most or all of other 9 species belonging to the genera, and moreover, γ-collidine always elicited an extremely strong response. In contrast, potassium chloride was a weak to moderate attractant only for a half of the strains tested. Palleroni's chemotactic method (Palleroni, N.J., Arch. Microbiol., 128, 53–55, 1980) for the isolation of motile actinoplanetes was complemented by using γ-collidine as a substitute for the originally used chemoattractant, potassium chloride, and by using humic acid-vitamin (HV) agar in place of the isolation medium, starch-casein agar. The improved method not only enabled the increased recovery of Actinoplanes spp. but also the consistent recovery of Dactylosporangium spp., which have only incidentally been isolated by the original method and by conventional dilution plating techniques, from various field soils (16 samples). The recovery of motile actinoplanetes was more successfully achieved by using HV agar supplemented with nalidixic acid to reduce associated bacterial contaminants.

Pollen-baiting and drying method for the highly selective isolation of Actinoplanes spp. from soil

A simplified enrichment method for the highly selective isolation of the zoosporic actinomycetes Actinoplanes spp. from soil is described. The method consists of baiting the species with Pinus pollen grains, desiccating (30°C, 2 h) the baits bearing sporangia in dried soil particles with the aid of silica gel and following the spore liberation upon immersion in water. Portions of the liquid enriched with zoospores are plated out on humic acid-vitamin (HV) agar supplemented with nalidixic acid at a concentration of 10 μg ml −1. The desiccation stage has enabled the almost complete elimination of associated bacteria from colonized baits while allowing the Actinoplanes sporangia to survive and still posses the ability to release many spores. A total of four different soil samples from fields of corn, peach, vegetable and paddy rice were examined. The pollen-baiting and drying method consistently resulted in the highly selective isolation of Actinoplanes spp. which accounted for over 83% of the total number of micro-organisms recovered on HV agar containing nalidixic acid.