Physical properties of blue-green algae: Ultracentrifugation and electron microscope studies

Summary

The Feulgen-positive and envelope-free nucleoplasm ofAnabaena andGloeocapsa contains DNA filaments. When ultracentrifuged it is displaced between the maze of photosynthetic lamellae to form a continuous, flattened layer in the centripetal half of the cell. The absence of a mesosome and lack of attachment of the nucleoplasm to the plasmalemma make the method of duplication and separation of the genome to the progeny an enigma. In the centripetal end of ultracentrifugedAnabaena, the photosynthetic lamellae are somewhat stretched and sometimes broken. This condition suggests that the cortical positioned photosynthetic lamellae are tightly connected in several places along their surfaces to an undisplaced cortical cytoplasmic layer. It is uncertain whether or not they are also directly attached to the plasmalemma. A vesicle is often observed in the centripetal end of the cell; it probably represents for the most part, the contents of distorted intralamellar spaces. In ultracentrifugedGloeocapsa, the photosynthetic lamellae show little displacement. They appear attached, probably at their ends to the plasmalemma and, likeAnabaena andNostoc, they possess phycobilisomes which are not greatly affected by ultracentrifugation. Cells usually survive a centrifugal force greater than required to separate most nonliving protein systems. When subcultured, a redistribution of the displaced components usually occurs and growth is resumed.