Aspergillus

Class: Acromycetes

Order: Aspergillales

Family: Aspregillaceae

Genus: Aspergillus

Aspergillus is a wide spread fungus generally saprophytic and growing stale bread , fruits, vegetables, jams, jellies, foot wear etc. a few species of Aspergillus are parasitic causing lung disease (aspergillosis) and ear infection (outomycosis).

The mycelium consists of a hyaline branched, septate and multi nucleated hyphae. Most of the mycelium grows above the substratum. Some hyphae grow deep into the substratum and halt in the distribution of nutrient and encouraged.

REPRODUCTION

ASEXUAL REPRODUCTION

Asexual reproduction

From the vegetative mycelium many un-branched erect, fertile hyphae called conidiophores arise from thick-walled cells called foot cells. These conidiophores form a swollen dawn shaped vesicles at the tips. The vesicles produce bottle shaped structure called sterigmata, which produces chains of conidia at their tips in basipital sub sessions. The sterigmata are multi nucleated and maybe found in two layers in some spices. The asexual spore called conidia are small , unicellular ,spherical structure with a double layer wall. The outer layer is called epispore/ exime, which is spiny and inner layer called the endospores/ intine. The conidial wall is pigmented with shapes of black, blue, green, yellow etc. depending upon the species. The conidia germinate by the production of germ tube and develop into new hyphae. The conidia are light weighted and carried by a wind.

SEXUAL REPRODUCTION

Sexual reproduction

It is by means of gametengial contact between the male antheridium and female ascogonium, which maybe produced on the same or different hyphae. Fertilization results in the formation of fruiting body called ascocarps, cleistothecium , which encloses a number of asci, each containing 8 ascospores, which when liberated germinates to give rise to a new mycelium.

ECONOMIC IMPORTANCE

A.niger also called the black mold is used in the industrial production of citric acid and glycolic acid.

A.flavus is known to produce a mycotoxin called aflatoxin.

Many species are important in food spoilage and some are known to cause disease.

Posted in: Microbiology