The ultrastructure of sporulation in Sporosarcina ureae

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Abstract
The morphology and ultrastructure of two strains of Sporosarcina ureae at various stages of growth and sporulation were examined by transmission electron microscopy. Sporulation begins with nonpolar cross wall growth as in vegetative division. Normal wall extension stops before complete septation, but membrane extension continues to completely bisect the cell. One of the cells so formed then engulfs the other by extension of the membrane. Germ cell wall and cortex material is then laid down, and the engulfed cell develops into a mature endospore in much the same way as in Bacillus species. After maturation, in broth cultures the spore remains in the mother cell. Lysis has not been observed over a period of several months. There are significant similarities between the phenotypic and ultrastructural characteristics of S. ureae and certain members of the species Bacillus suggesting a close phylogenetic relationship.