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Microconidial  state of  Fusarium

Many Fusarium species have two different conidial states.  The classical Fusarium spore (macrospore or macroconidium) is referred to as boat-shaped, often like a high prowed Gondola.   Fusarium also sometimes possesses  much smaller spores (microspore or microconidium).  Both types of spores are phialidic (arising in succession, youngest at the base, from an open-mouthed conidiogenous cell = phialide).  In  microconidial Fusarium the spores are produced in succession  and are in a mucoid slime;  so they slip down by gravity to form a ball at the tip of the simple (unbranched) conidiogenous cell (spore mother cell).

To confuse matters further, some Fusarium species also produce thick-walled resting spores (chlamydospores) either in the vegetative hyphae or sometimes directly in the cells of the multiseptate macroconidium!  To check what a chlamydospore looks like click here.

To top the lot some Fusarium species also have a sexual state (teleomorph) that produces an ascoma (perithecium) with asci and ascospores that are shot off at maturity e.g. Gibberella.     Mostly when isolating fungi it is the Fusarium state that you find in cultures.  The perithecial state is rarely found without special efforts.

STUDENTS

1. Present a reasonable hypothesis to explain why Fusarium 'needs' so many different spore types.

Hint: Write down the advantages and disadvantages of each spore type as you perceive them.  Use your imagination and think like a fungus!

2. How would you distinguish microconidial Fusarium from Acremonium (Cephalosporium)?

3. What do you know about Fusarium and eye infections in humans?