Abstract
A new method was developed to isolate actinomycetes from soil more selectively and more thoroughly.
Elements of the procedure are (1) treatment of soil suspension with a solution containing yeast extract (YE) 6% and sodium dodecyl sulfate (SDS) 0.05%, at 40°C for 20 min, (2) subsequent dilution with water and (3) a few week’s incubation on HV agar plates containing nalidixic acid (n.a.) 20 mg/L.
The YE and the heat shock at 40°C activated spore germination of a variety of actinomycete strains, the SDS acted as a germicide only on bacterial cells with rare exception, and the n.a. suppressed growth of bacterial spore formers without any effect on the actinomycetes, under the conditions used.
By the treatment of soil suspension with YE and SDS, the count of actinomycete cfu per g. of various soils (10 samples) was increased by 40% and the count of bacteria was decreased to 20%, on the averages. The bacterial count was further decreased to less than 10% by addition of n.a. into the isolation medium.
