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Howard Judelson's background
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The oomycetes
learn more about these exciting organisms

The late blight disease
learn more about the problems that P. infestans causes

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The Oomycetes

P. infestans is a member of the oomycetes. Oomycetes are a large collection of important species that include both saprophytes and significant parasites of plants (Pythium, Phytophthora, white rusts, downy mildews), animals, and insects. Oomycetes lack taxonomic affinity with the so-called true fungi (i.e. ascomycetes and basidiomycetes). Instead, oomycetes are classified with diatoms and brown algae in a group called the Stramenopiles. The oomycetes are the largest group of Stramenopiles, and are found worldwide in fresh and salt water habitats. Most oomycetes grow as 'fungal-like' filaments, or hyphae, although there are exceptions.

tree of life
Oomycetes show little affinity with true fungi.
Tree adapted from NY Times 8/99


Reflecting the taxonomy of the oomycetes, processes appearing similar between oomycetes and true fungi are consequently very different genetically and biochemically. The cell walls of the group are also unique, consisting mostly of beta-1,3- and beta-1,6-glucans and cellulose. Most members of the group are filamentous and lack septa except where reproductive cells are produced, such as the spores. All oomycetes are diploid in the vegetative phase with meiosis occurring during gametogenesis.

Unfortunately, oomycetes have been understudied compared to true fungi. P. infestans presents a good system for remedying this deficiency since it is amenable to genetic and biochemical manipulations and is easily grown, unlike many oomycetes.

Although our lab focuses on oomycetes that are plant pathogens, many oomycetes are important animal pathogens. Some examples of oomycetes that are pathogenic on species other than plants include: Pythium insidiosum, which infects animals ("swamp cancer"); Lagenidium giganteum, which parasitizes the larval stage of mosquitoes and is being used as a potential control agent; and Saprolegnia, which infect several species of fish.


stramenopiles
The large size differences between the different members of the stramenopiles provides one indication of the great biological diversity within the kingdom!


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updated 6.7.17