Ophiocordyceps unilateralis

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A Microbial Biorealm page on the genus Ophiocordyceps unilateralis

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Classification

| Fungi | Ascomycota | Sordariomycetes | Hypocreales | Ophiocordycipitaceae | Ophiocordyceps | O. unilateralis | Ophiocordyceps unilateralis

Description and Significance

Ophiocordyceps unilateralis is a fungal pathogen specifically infecting Camponotus leonardi of the tribe of campotini. Although O. unilateralis may infect ants of another species behavioral manipulation observed in other species were not as consistent. Once infected the ants will climb down from their natural habitats on rainforest tree and relocate to 25 cm off the ground under leaves where the temperature is low and humidity is high. Spores of O. unilateralis are actively discharged and dispersed over short distances, creating an infectious “killing field” of ∼1 m2 below the dead host (N. L. Hywel-Jones, unpublished data).


Genome Structure

The genome of this organism is not sequenced entirely, although major enzymes such as RNA polymerases have been sequenced. Four polyketide synthase (PKS) genes have been found in O. unilateralis. PKS enzymes synthesize polyketide proteins, which have proven to be novel antibiotics, antifungal agents, and even cholesterol lowering agents.

Ophiocordyceps unilateralis

Cell Structure and Metabolism

There are three distinct phases of life for Ophiocordyceps unilateralis. The first is ascospore formation and germination, where they are deposited on the hopeless ants and a projection called a germ tube goes into the insect (Wongsa). The ascospores are around 20-100 um in length, and skinny. The second phase is the yeast-like phase, where eventually a mycelium is made (Wongsa). The cells start off looking like individual yeast cells, which then come together to branch out, forming the mycelium (a common structure among fungi). The third phase is penetration of the insect's cuticle by the newly formed stalk to sporulate and begin the process of infecting more ants (Wongsa).

As for metabolism,

Ecology

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Pathology

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Current Research

Current research is being done on the possibility that the organism could contain novel chemicals of medicinal use to humans. One of the more interesting recent findings was the presence of anti-malarial naphthoquinones within the organism (citation needed).

Cool Factor

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References

Wongsa P, Tasanatai K, Watts P, Hywel-Jones N (2005) Isolation and in vitro cultivation of the insect pathogenic fungus Cordyceps unilateralis. Mycol Res 109:936–940.

Amnuaykanjanasin A, Phonghanpot S, Sengpanich N, Cheevadhana- rak S, Tanticharoen M (2009) Insect-specific polyketide syn- thases (PKSs), potential PKS-nonribosomal peptide synthetase hybrids, and novel PKS clades in tropical fungi. Appl Environ Microbiol 75(11):3721–3732.