A METHOD FOR THE SELECTIVE ISOLATION OF MYXOCOCCUS DIRECTLY FROM SOIL

A new method is described for the selective isolation of species of My xococcus directly from soil by dilution plating. The method involves s uppression of competing microorganisms with antibiotics combined with air drying and wet heat treatment of soils. Fungi were eliminated by s upplementing the plating medium with cycloheximide and nystatin, Non-s porulating bacteria were controlled by air drying soils and then heati ng aqueous soil dilutions for 10 min at 56 degrees C. The predominant sporulating bacteria in soil, Streptomyces acid Bacillus, were suppres sed by adding either tiacumicin B, ristocetin or vancomycin to the med ium. Swarming of Myxococcus colonies was controlled with a casein dige st-yeast extract plating medium (CY-C10 agar), Ultrasound treatment of soil suspensions gave the highest number of Myxococcus colonies in th e soils studied, but these cultures could be recovered without ultraso und. Strains of Myxococccus fulvus, M. xanthus, M. coralloides, M. sti pitatus and M. virescens were isolated from soil using this technique. Soils examined yielded one or two Myxococcus species per sample.