Also found in: Dictionary, Thesaurus, Medical.
a sporiferous bacterium of the family Bacil-laceae. It is widespread in nature—in soil, on plant raw material, in airborne dust, and on the surface of food products. The rod-shaped vegetative cells of the hay bacillus are 2–3 microns long and 0.4 microns thick. They are gram-positive, reproduce by division, and have flagella over their entire surface. The spores are oval and located in the center of the cell. To isolate cultures of the hay bacillus, an infusion of hay is boiled. All the microbes are killed except the spores of the hay bacillus, which are resistant to high temperatures and capable of growing later. The hay bacillus is an obligatory aerobe. On the surface of a fluid nutrient medium it forms a thin whitish film; on the surface of a solid medium it forms colonies, which are rounded, grayish, smooth, and shiny. The hay bacillus belongs to the ordinary saprophytes, which decompose organic matter (carbohydrates and proteins). It often causes food spoilage, but it is nonpathogenic.