KINETOPLAST AND OTHER SATELLITE DNAs OF KINETOPLASTIC AND DYSKINETOPLASTIC STRAINS OF TRYPANOSOMA

Members of the protozoan order Kinetoplastida (Honigberg et al., 1964), which includes the genera Trypanosoma, Leishmania, and Crithidia, are characterized by the presence of a body known as a kinetoplast. The kinetoplast is a modified region of a mitochondrion (Meyer et al., 1958; Steinert, 1960; Clark and Wallace, 1960) which contains so much DNA that it can be detected by Feulgen staining (Bresslau and Scremin, 1924). DNA isolated from a kinetoplast fraction of Trypanosoma lewisi was found to have a buoyant density less than that of the cell's nuclear DNA and to comprise mainly covalently closed, circular molecules 0.4 ,u in contour length, and some noncircular molecules (Renger and Wolstenholme, 1970). A proportion of the circular DNA was in the form of catenanes in which many circles were apparently interlocked with one or more adjacent circles. A DNA separated from whole cells of Trypanosoma cruzi, and presumed to be kinetoplast DNA, had similar properties (Riou and Paoletti, 1967; Riou and Delain, 1968). Also, circular molecules 0.74 ,. long were found to be included in DNA from a kinetoplast fraction of Trypanosoma mega (Laurent and Steinert, 1970). Loss of kinetoplast DNA from cells of a number of species of Kinetoplastida following treatment with diphenylamine compounds or with one of a number of basic dyes has been reported (Werbitzki, 1910; Miihlpfordt, 1959, 1963 a, 1963 b, 1964; Trager and Rudzinska, 1964; Guttman and Eisenman, 1965; Steinert and Van Assel, 1967; Simpson, 1968; Riou, 1968; Renger and Wolstenholme, 1970). Such organisms are usually referred to as dyskinetoplastic (Trager and Rudzinska, 1964). Dyskinetoplastic ells of in vitro culture strains cannot be maintained indefinitely. However, a few species of trypanosomes, all members of the so called brucei group (Hoare, 1964), can still be maintained in the blood of the vertebrate host after apparent induced loss of their kinetoplast DNA (for a review see Miihlpfordt, 1964). Two dyskinetoplastic strains, Trypanosoma equiperdum and