Scanning and transmission electron microscopy of three strains of Bifidobacterium.

Scanning and transmission electron microscopy was applied for a morphological study of three strains of Bifidobacterium grown on solid or liquid media. The pronounced pleomorphism of the cultures previously observed by light microscopy was confirmed. A possible sequence of the morphological events during transformation from one to another pleomorphic form is proposed for B. bifidum and B. longum. Ultrastructural differences such as the formation of extensive mesosomal complexes in B. longum and characteristic plasmalemma particles only observed in the B. bifidum mutant are described and discussed.