Kinetoplastea

Abstract

The class Kinetoplastea Cavalier-Smith 1981 (previously known as the order Kinetoplastida Honigberg 1963) constitutes an important group of free-living and parasitic flagellates. The group is named after the kinetoplast, a unique cell organelle consisting of the tightly packaged mitochondrial DNA, which forms a stainable structure within the single mitochondrion. The Kinetoplastea includes several important human pathogens that are carried by bloodsucking insect vectors, e.g., Trypanosoma brucei, T. cruzi, Leishmania donovani, L. major, and L. tropica, as well as vector-borne animal pathogens such as the African tsetse-transmitted trypanosomes that cause nagana. Some kinetoplastids are plant parasites, e.g., Phytomonas, transmitted by phytopha- gous bugs. While these pathogenic kinetoplastids are of major medical, veter- inary, and economic importance, many other kinetoplastid species also have a parasitic lifestyle, either in a single host species or alternating between two different hosts. The ubiquitous free-living kinetoplastids such as Bodo are of major ecological importance as heterotrophs in marine and freshwater envi- ronments. Some kinetoplastid species are popular and significant laboratory model species for biochemical and molecular biology investigations. In par- ticular, Trypanosoma brucei is notorious for its ability to undergo antigenic variation, and Leishmania infection is a paradigm for T-helper cell type I and type II immune responses.