High-resolution scanning electron microscopy of chromatin bodies and replication bands of isolated macronuclei in the hypotrichous ciliate Euplotes aediculatus

Abstract

Summary We observed isolated and demembranated macronuclei of Euplotes aediculatus with a field emission scanning electron microscope (JEOL JSM-6401F) to examine three-dimensional surface structures of chromatin bodies and the replication band. Freezing and thawing in 0.25 M sucrose followed by treatment with 1% acetic acid demembranated the isolated macronuclei. Each macronucleus was composed of a large number of granular chromatin bodies of various sizes (0.2–1.0 μm in diameter). Despite their size variation, each chromatin body was composed of small granules (uniform diameter of ca. 50 nm) with frequent filamentous bridge connections to neighboring chromatin bodies. On the replication band, the chromatin bodies were disintegrated into their component 50 nm granules. In some areas, the surface was observed to be composed of smaller particles of ca. 10 nm in diameter.