Electron microscopic identification of RNA- and DNA- containing structures in the preparations of isolated macronuclei of ciliates Bursaria truncatella

RNAand DNA-containing structures in the ciliate Bursaria truncatella were studied on ultrathin sections and spread preparations of individual macronuclei isolated at middle interphase. To label DNA-containing structures we used antiDNA antibodies and protein A-colloidal gold complexes. To label RNP structures, complexes of gold with RNase A were used. Chromatin structures in the form of accumulations of nucleosome fibrils, partially decompacted or compact chromatin bodies were effectively labeled with anti-DNA antibodies. The accumulations of nucleosome fibrils were shown to be heterogeneous. Some of them corresponded to partially or completely decompacted inactive chromatin bodies, while others – to active chromatin. The latter contained granules of various sizes (20-50 nm) labeled with RNase-gold. The data obtained also showed that homogeneous accumulations of 20-30 nm granules, which often intermingled with accumulations of nucleosome fibrils, corresponded to nucleolar granular component. Such accumulations were in close contact with nucleosome fibrils, which points out the close connection between nucleolar structures and chromatin in macronuclei of B. truncatella.