Comprehensive Description

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General Description

Conidiobolus coronatus is a ubiquitous saprobe of plant debris. It is an opportunistic pathogen and in humans it is the major causative agent of rhinoentomophthoromycosis. Rhinoentomophthoromycosis is the condition of having an Entomophthorales fungus in the nose. This word has four roots. Rhino comes from rhinos which meant nose in Greek. Entomophthoro comes from the fungal order Entomophthorales . Myco is Latin for fungus and sis stands for condition of.
 C. coronatus has been known to parasitize other mammals, such as horses, llamas, dolphins, and chimpanzees. It was first described by Costantin in 1897 in France and was first isolated in 1961 by Chester Emmons and Charles Bridges from nasal granulomata of three horses in Australia. A granulomata is a bulge that forms because the cells of the immune system attempts to wall off the fungus. In 1965, Bras et al discovered and isolated the first human case in the Caribbean on the Grand Cayman Island.
 C. coronatus is also an opportunistic parasite of many insects and it has been proposed as an insecticide. An insecticide is either a chemical or an organism that can kill insects that damage crops. C. coronatus infects a large variety of insects; however it is an especially effective parasite of Lepidoptera, which is the family that includes butterflies and moths.
  C. coronatus lacks an apparent sexual life cycle because it is heterothallic and does not produce zygospores. However, the asexual life cycle is very complex. When, primary conidia are produced from the hyphae, the columella projects into the conidia. The primary conidia are released by an eversion mechanism which is characteristic of the genus Conidiobolus. Due to turgor pressure the conidia release and both the bottom of the conidia and the tip of the conidiophore project. The primary conidia are globose, multinucleate, and have two cells walls that are connected. The primary conidia can germinate by forming hyphae from multiple germ tubes. In addition, the primary conidia can germinate by repetitively forming into secondary conidia. The secondary conidia are oriented by light and are also released by eversion. There are various forms of secondary conidia. The primary conidia can produce short conidiophores containing microconidia which form on multiple sterigmata. The microconidia allow greater dispersal. In addition, there are various secondary resting spore types observed such as villose conidia, chlamydospores, and locriconidia. Resting spore allow survival in unfavorable growth conditions. C. coronatus is unique in its genus because it produces villose conidia, from which it gets its name because the spikes look like those of a crown, and microconidia. Oddly, when Costantin first described C. coronatus he did not observe the villose spores.
 Secondary conidia production is regulated by the availability of nutrients and pH. Nutrient rich or mildly acidic or basic medium produces germination of germ tubes to form hyphae, while nutrient poor or extremely acidic and basic medium will lead to the production of secondary conidia. Younger cultures and cultures in humid environments tend to produce the microconidia, while older cultures tend to produce the villose conidia.



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© Grant Justin

Source: Mushroom Observer

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