New classification of eukaryotes has implications for AIDS treatment, agriculture and beyond

October 25, 2005

This classification conveys important information about the biochemistry and metabolism of disease-causing organisms. Here are three examples. 1) Pneumocystis, an opportunistic pathogen causing mortality in AIDS patients and immunocompromised individuals, is now known to be a fungus, indicating a different treatment regimen is needed. 2) Phytophtora, an organism causing potato blight, such as the one that caused the Irish famine in the 19th century, is now known not to be a fungus, which explains why fungicides are not effective treatments. 3) Plasmodium, the causative agent of malaria, is now known to share ancestry with photosynthetic organisms and has a vestigial chloroplast, called the apicoplast. This knowledge opens exciting possibilities for novel drug therapies.

The new classification recognizes 6 major clusters of organisms, rather than the 4 traditional Kingdoms. These clusters are 1) the Opisthokonta, grouping the animals, fungi, choanoflagellates, and Mesomycetozoa; 2) the Amoebozoa, grouping most traditional amoebae, slime moulds, many testate amoebae, some amoebo-flagellates, and several species without mitochondria; 3) the Excavata, grouping oxymonads, parabasalids, diplomonads, jakobids, and several other genera of heterotrophic flagellates, and possibly including the Euglenozoa and Heterolobosea; 4) the Rhizaria, grouping the Foraminifera, most of the traditional Radiolaria, and the Cercozoa with filose pseudopodia, such as many amoebo-flagellates and some testate amoebae; 5) the Archaeplastida, grouping the Glaucophyta, red algae, green algae, and Plantae; 6) the Chromalveolata, grouping the Alveolata (including ciliates, the dinoflagellates, and the Apicomplexa), cryptophytes, haptophytes, and stramenopiles (including brown algae, the diatoms, many zoosporic fungi, opalinids, amongst others).

Finally, the authors noted that they "adopted a hierarchical system without formal rank designations, such as "class," "sub-class," "super-order" or "order," The decision to do so has been primarily motivated by utility, to avoid the common problem of a single change causing a cascade of changes to the system. We believe this to be more utilitarian, and less problematic than traditional conventions, as it is not constrained by formally attributing a limited number of rank names."
-end-
This study is published in the current issue of The Journal of Eukaryotic Microbiology. Media wishing to receive a pdf of this article, please contact journalnews@bos.blackwellpublishing.net

About the Corresponding Authors
Dr. Sina Adl is currently a professor of biology at Dalhousie University, and an expert on the microbiology of soil organisms, particularly protozoa. He coordinated this multi-authored classification and has a broad knowledge of eukaryotic diversity. He can be reached for media questions and interviews.

Dr. Denis H. Lynn is currently a professor of biology at the University of Guelph. He is Editor in Chief of The Journal of Eukaryotic Microbiology, Chair of the Committee on Systematics and Evolution of The International Society of Protistologists, and an expert on the evolution and ecology of ciliated protozoa. He can be reached for media questions and interviews.

About The Journal of Eukaryotic Microbiology
The Journal of Eukaryotic Microbiology publishes original research on protists, including lower algae and fungi. Articles are published covering all aspects of these organisms, including their behavior, biochemistry, cell biology, chemotherapy, development, ecology, evolution, genetics, molecular biology, morphogenetics, parasitology, systematics, and ultrastructure.

About The International Society of Protistologists
The International Society of Protistologists is an international group of researchers who share one thing: protists as research organisms.

Society members' areas of research are diverse, ranging from ecology and evolution to genetics and parasitology to the search for life elsewhere. Protists are often making headlines, from harmful algal blooms to malaria to research on aging, and the society is in step with these developments.

For more information and to find out how to become a member, visit the International Society of Protistologists website.

Blackwell Publishing Ltd.

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