Ultrastructural analysis has been carried out on three Leishmania isolates which are proven causal agents of human cutaneous Leishmaniasis, L. tropica major, L. aethiopica and a unidentified species, Leishmania SP48. No significant differences in submicroscopic morphology have been found in thin-sectioned organisms from the three isolates. Extensive plate cristae have been observed within the mitochondria and connections between the rim of the kinetoplast nucleoid and the inner mitochondrial membrane noted. Kinetoplast DNA (kDNA) has been isolated from these isolates and from L. tarentolae and examined by protein monolayer spreading and darkfield electronmicroscopy. The basic molecular arrangement of isolated kDNA in the form of 5 micrometers networks of 0.28--0.3 micrometer mini-circles with long looped DNA in the interior and at the periphery of networks is similar in all isolates. Minor differences between L. aethiopica and SP48 compared with L. tropica major have been observed. The kDNAs of L. aethiopica and SP48 are identical morphologically. Buoyant density analysis has shown that kDNA from L. aethiopica and SP48 have identical values and these are different from the values for L. tropica major. The finding of similar buoyant densities for kDNA from L. tropica major and L. tarentolae also imply a sequence homology by this criteria which is refuted by the results given in the following paper. The results given in this and the following paper (Arnot, D.E. and Barker, D.C.(1981) Mol. Biochem. Parasitol. 3, 47--56 indicate that the unknown Leishmania SP48 is very closely related to, if not identical with, L. aethiopica. This finding is consistent with the clinical and ecological facts known for the organism SP48.
- kinetoplast DNA
- darkfield electron micrograph
- buoyant densities