LEISHMANIA-MAJOR - PARASITE INTERACTIONS SUGGESTING SEXUALITY

In Jive experiments, Leishmania (Leishmania) major (MRHO/SU/59/P-strai n) grew poorly when seeded in FYTS medium supplemented with 15% fetal calf serum, but presented several peculiar pairs of promastigotes diam etrically opposed and attached at their posterior ends (5.8-13.5%). As seen in Giemsa-stained smears, a ring-like line and/or an enlargement , generally occurred at the parasite junction. A close proximity of nu clei, which sometimes were difficult to distinguish Sr om each other; was also observed at this junction. Several of these pairs appeared to be composed of fused cells in which the nuclei could be apparently fu sed, as shown by fluorescence microscopy to detect beta-tubulin and DN A, and bit scanning electron microscopy. Under other culture condition s these pairs were absent or occurred at very low rates (0.2-2.2%). Su ch pairs differ markedly from longitudinally dividing cells and resemb le those described in two other Leishmania species, as well as in Herp etomonas megaseliae and Phytomonas davidi, suggesting steps of a putat ive sexual process.