Ultrastructural Studies of Spores and Hypha of a Glomus Species

The ultrastructure of spores and hyphae of a Glomus isolate (INVAM-906/312); structure and development are described with both light and transmission electron microscopy. The spore wall is formed by two layers in one group; the outer is evanescent and formed by an amorphous matrix, whereas the inner wall layer is laminated and has fibrils that seem to be arranged in an arcuate pattern as observed in other glomalean spores. The spore has a more complex wall structure than hyphae. The content of both spore and hyphae also differs regarding the presence and distribution of lipid globules, vesicles, and other structures. Intracytoplasmic bacterium-like organisms (BLOs) were observed in spores and germ tubes; some of these BLOs were apparently undergoing binary fission.