The Cytology and Life-cycle of Azotobacter chroococcum

Abstract

SUMMARY: Azotobacter chroococcum exists in two cytologically distinct vegetative forms. In one the appearance is that of a typical bacterial resting cell, with a large vesicular nucleus. In the other the cytoplasm appears homogeneously vacuolated and refractive; this is correlated with a high lipid content. Gonidia of two types are produced from the nucleated cells. The more common are tiny bacilli with polar flagella; these are released from the lumen of the mother cell and reproduce by fission. Larger gonidia, resembling miniature vegetative cells, develop within the mother cell, which becomes greatly elongated. These large gonidia do not appear to divide but grow directly into vegetative cells. Mother cells of both kinds may be Grainpositive.