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The histopathology of Entomophaga grylli pathotype 2-infected tissues was investigated. Fat body, male reproductive system, gastrointestinal tract, central nervous system, and skeletal muscle of infected and uninfected grasshoppers were compared to determine the pathological events during the infection. The pathotype 2 protoplasts adhered to fat body and penetrated neural tissue early in the infection, whereas the skeletal muscle was penetrated after host death. Ultrastructural examination of infected fat body suggested one contributing cause of death was nutrient depletion.

Light and electron microscopic observations were made of protoplast changes during Entomophoga grylli pathotype 2 infections of Melanoplus differentialis. Protoplast development was divided into three stages: amoeboid, developing, and mature protoplasts. Each stage was characterized by changes in protoplast and organelle morphology. Amoeboid protoplasts were amoeboid in shape, exhibited movement, and contained very few lipid droplets. Developing and mature protoplasts were rounded in shape and contained increasing amounts of lipid droplets. Morphological changes were also observed in dense bodies, nuclei, and cell membrane as the protoplasts matured.

(1980). Ultrastructure, Physiology, and Biochemistry of Bacillus Thuringiensis. CRC Critical Reviews in Microbiology: Vol. 8, No. 2, pp. 147-204.

A B S T R A C T The spore wall of the myxomycete, Physarella oblonga, requires only 1 hr to develop. The spore wall surface ornamentations, the warts, are secreted first, followed by an outer electrondense layer and an inner electron-lucent layer. A measurement analysis was conducted to determine if vesicles were involved in wall elaboration. By comparing spore plasmalemma length to the number of fused vesicles, a semi-quantitative analysis can be obtained. The determination reveals that very few vesicles are associated with wart and outer wall development. The greatest number of vesicles are associated with inner wall secretion. Plasmalemmasomes are most numerous during outer wall formation and Golgi bodies are observed only during inner wall elaboration. Other organelles do not seem directly involved in wall secretion. ULTRASTRUCTURAL INVESTIGATIONS of myxomy

Transmission electron micrographs of glutaraldehyde- OsO 4 -fixed Rhizobium trifolii 0403 before and after cells were treated with 16.6 mM succinate showed that treated cells increased in mass by increasing cytoplasmic volume. The morphology of succinate-treated cells was identical to that of bacteroids, and the appearances of the envelope and periplasmic space were similar. The primary difference was in inclusion number and type.

A comprehensive ultrastructural analysis of sporulation and parasporal crystal development is described for Bacillus thuringiensis . The insecticidal crystal of B. thuringiensis is initiated at the start of engulfment and is nearly complete by the time the exosporium forms. The crystal and a heretofore unobserved ovoid inclusion develop without any clear association with the forespore septum, exosporium, or mesosomes. These observations contradict previous hypotheses that the crystal is synthesized on the forespore membrane, exosporium, or mesosomes. Formation of forespore septa involves densely staining, double-membrane-bound, vesicular mesosomes that have a bridged appearance. Forespore engulfment is subpolar and also involves mesosomes. Upon completion of engulfment the following cytoplasmic changes occur: decrease in electron density of the incipient forespore membrane; loss of bridged appearance of incipient forespore membrane; change in stainability of incipient forespore, forespore, and mother cell cytoplasms; and alteration in staining quality of plasma membrane. These changes are involved in the conversion of the incipient forespore into a forespore and reflect “commitment” to sporulation.