Isolation and partial characterization of mutants of the trypanosomatid Crithidia fasciculata and their use in detecting genetic recombination.

Crithidia fasciculata was used as a model trypanosomatid to study the possible existence of genetic recombination in this group of protozoa. The approach was based on the ability to select a variety of mutants on agar plates. Following mutagenesis of wild type cells by nitrosoguanidine or ethylmethanesulfonate, stable mutant phenotypes were obtained. These included mutants resistant to the drugs actinomycin D, 6-azauracil, 6-azauridine, and 5-fluorouracil, auxotrophs and colony morphology mutants. Following mixed growth of pairs of drug-resistant mutants on selective media, isolates exhibiting stable recombinant phenotypes were obtained. The data presented suggest that 1) Crithidia undergoes some type of genetic recombination and 2) Crithidia must be diploid at some time during this process.