Soil bacteriostasis: inhibition of spore germination and microcolony development in agar discs incubated on nonsterile soils.

An agar-disc method showed that bacterial spores were subject to a bacteriostatic effect exerted by soil. Soil either inhibited spore germination or reduced microcolony development of the six Bacillus strains tested. Bacteriostasis was relieved by the addition of nutrients to soil-exposed discs after they had been removed from the soil.