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The oomycetes: A unique group of eukaryotic pathogens

Oomycetes are fungus-like Stramenopiles

The oomycetes form a diverse group of fungus-like eukaryotic microorganisms, also known as water molds, that include saprophytes as well as pathogens of plants, insects, crustaceans, fish, vertebrate animals, and various microorganisms. A multitude of saprophytic oomycetes primarily inhabit aquatic and moist soil habitats and play key roles in decomposition and recycling of organic matter. However, plant pathogenic species, notably those of the genus Phytophthora, are the best studied oomycetes. Species of the genus Phytophthora (the 'plant destroyer' in Greek) are arguably the most devastating pathogens of dicotyledonous plants. They cause enormous economic damage on important crop species such as potato, tomato, pepper, soybean, and alfalfa, as well as environmental damage in natural ecosystems. Virtually every dicot plant is affected by one or more species of Phytophthora, and several monocot species are infected as well.

Traditionally and due to their filamentous growth habit, oomycetes have been classified in the Kingdom Fungi. However, modern molecular and biochemical analyses indicate that oomycetes share little taxonomic affinity to fungi, but rather form a diverse and well defined group of eukaryotes with affinities to brown algae and diatoms. Subsequently, oomycetes are now classified as Stramenopiles, one of several major eukaryotic Kingdoms.

Oomycetes cause devastating diseases

The oomycetes comprise numerous destructive plant pathogens, including over 60 species of the genus Phytophthora, several genera of the biotrophic downy mildews, and more than 100 species of the genus Pythium. Many of these pathogens cause devastating diseases on several crop and ornamental plants that are notoriously difficult to manage. Other oomycetes cause economically important diseases in animals.

Plant diseases caused by oomycetes

Animal diseases caused by oomycetes

Review articles on oomycetes

Lamour, K, Win, J., and Kamoun, S. 2007. Oomycete genomics: new insights and future directions. FEMS Microbiology Letters, 274:1-8.

Haldar, K., Kamoun, S., Hiller, L. N., Bhattacharjee, S., and and van Ooij, C. 2006. Common infection strategies of pathogenic eukaryotes. Nature Reviews Microbiology, 4:922-931.

Kamoun, S., and Smart, C.D. 2005. Late blight of potato and tomato in the genomics era. Plant Disease, 89:692-699.

Kamoun, S. 2003. Molecular genetics of pathogenic oomycetes. Eukaryotic Cell, 2:191-199.