kinetoplastids

Kinetoplastids are a group of flagellated, unicellular eukaryotes within the class Kinetoplastea of the phylum Euglenozoa. They are distinguished by a distinctive mitochondrial DNA structure called a kinetoplast, which forms a compact network inside a single large mitochondrion.

The kinetoplast is a DNA-containing organelle composed of maxicircles and numerous minicircles. The network is closely associated with the basal body of the single emergent flagellum. Kinetoplasts house RNA editing machinery: many mitochondrial transcripts require insertion or deletion of uridines guided by small RNAs (gRNAs) encoded by the minicircles. This editing can be extensive and is essential for mitochondrial gene expression in several species.

Kinetoplastids include both free-living and parasitic genera. Notable parasitic groups are the trypanosomatids, which include Trypanosoma and Leishmania species. Free-living kinetoplastids such as Bodonidae also occur in aquatic environments. Members typically possess a single flagellum with a distinctive flagellar pocket used for feeding and locomotion. They often rely on glycolysis in glycosomes, specialized peroxisome-like organelles, and can have variable mitochondrial activity depending on life stage.

Many kinetoplastids have complex life cycles involving invertebrate vectors and vertebrate hosts. Disease-causing species include Trypanosoma brucei (African sleeping sickness), T. cruzi (Chagas disease), and Leishmania spp. (leishmaniasis), transmitted by tsetse flies, triatomine bugs, and sandflies, respectively. Other kinetoplastids are non-pathogenic or opportunistic environmental organisms.

Kinetoplastids provide key insights into mitochondrial organization and RNA editing and represent a diverse lineage of protists with significant medical and ecological relevance.