Nuclear Morphology of Bacillus cereus grown on Partially Defined Media

Summary: When Bacillus cereus was grown on a medium solidified with agar but of otherwise known composition (salts, glucose, urea) impression preparations made after 2½ hr. of growth at 30° showed simple round nuclei by the osmic acid-hydrochloric acid-Giemsa technique. Similarly treated preparations made after 24 hr. of incubation showed well-marked unstained refractile inclusions. These inclusions, whose lipid nature was indicated by staining with Sudan Black, were closely associated with nuclear material, often appearing to be surrounded by an unbroken ring, a granular band, or a horse-shoe shape of nuclear material. These observations support the suggestion of Delaporte (1950) that lipid inclusions may distort nuclear shapes. These distortions might be misinterpreted as mitotic figures.