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.