ON THE DNA CONTENT AND PLOIDY OF TRYPANOSOMES

The nuclear and kinetoplast DNA content of 2 trypanosomatids was determined by quantitative absorption and fluorescence cytophotometry of individual Feulgen-pararosaniline stained cells. For the insect trypanosomatid Crithidia fasciculata nuclear and kinetoplast DNA contents of 0.095 and 0.032 pg per non-replicating cell were found. For the African trypanosome Trypanosoma brucei these values are 0.097 and 0.004 pg. A sub-population of T. brucei cells with 2 kinetoplasts and 1 nucleus was found to contain 0.181 pg/nucleus. The DNA values of bloodstream from T. brucei and the procyclic culture form were not significantly different. In DNA-DNA renaturation experiments the haploid amount of DNA in T. brucei was previously found to be 0.041 pg/nucleus. T. brucei is apparently diploid. No sub-population of haploid cells was observed in T. brucei grown in rats or in culture.