Ultrastructure of Dormant and Germinating Conidia of Aspergillus Ochraceus

ABSTRACT

Ultrastructural changes during germination of Aspergillus ochraceus conidia were studied. The following ontogenetic stages were observed: 1) dormant state; 2) hydration and expansion; 3) aggregation; and 4) germ tube formation. The dormant spore possessed a dehydrated cytoplasm enclosed by a wall consisting of an inner, relatively electron-transparent zone and an outer electron-opaque zone. This wall in turn was surrounded by an outer, wrinkled layer that contained the rodlet region. Spore expansion was accompanied by formation of a new inner wall layer continuous with the germ tube wall formed during germination. Overlapping in time with formation of the new wall was development of a substance that formed a fibrillar sheath about the spore. The sheath was responsible for spore aggregation as germination progressed. Generally, a single germ tube emerged from each conidium and was surrounded by a fibrillar sheath continuous with the sheath surrounding the spore. Numerous vesicles were located at the tip of the germ tube.

Key Words:

• Aspergillus
• conidia
• spore germination
• ultrastructure