A simple chemically defined medium containing sodium acetate (37 or 74 mM) as the only major source of carbon was inoculated with soil from various locations. The bacteria which grew most rapidly at 30 degrees C were almost entirely strains of Bacillus sphaericus and Arthrobacter species. Pasteurization of the soils made the medium selective for B. sphaericus. Several new strains were isolated, and the peptidoglycans of their cell walls were examined.
