[Biology Class Notes] on Deuteromycetes Pdf

Commonly called molds, Deuteromycetes are “second-class” fungi carrying no sexual state in their life cycle, reproduced only by producing spores via mitosis. This state of asexual fungi is called Anamorph. In other words, this imperfect fungi class falls under artificial fungi, of which there are approximately fifteen thousand species because of the asexual reproductive mechanism.

Deuteromycetes are also known as Deuteromycota, Deuteromycotina, fungi imperfecti, and mitosporic fungi.

Reproduction in Deuteromycetes

The reproduction phase in Deuteromycetes takes place in different forms. Spores or Conidia is one such form produced directly on the mycelium or on the structure of specialized mycelial cells called Conidiophores. Some forms of these Deuteromycetes don’t produce spores. Moreover, non-sporulating fungi are able to propagate themselves by fragmenting the hyphae or by producing a mass of hyphae called a sclerotium. Sclerotia can be microscopic in size or as large as several millimetres in diameter.

Characteristics of Deuteromycetes

• Deuteromycetes fungi carry some salient features that make them worth studying.

• Deuteromycetes occur as saprophytes on a wide range of substrates, but a large number of these fungi are parasites on plants and animals. This causes a variety of diseases. Leaf- spots, blights, blotch, wilts, rots, anthracnose, etc. are the important diseases of plants, while diseases like meningitis, candidiasis, skin diseases, nail diseases, and others are caused in animals.

• The mycelium is made up of profusely branched and septate hyphae posing multinucleate cells and simple pore septa.

• The hyphae may be intracellular and their cell wall chiefly contains chitin-glucan.

• Deuteromycetes reproduce only asexually. This method of asexual reproduction takes place by hyphal fragments, budding, arthrospores (flat-ended asexual spores formed by the breaking up of cells from the hypha), chlamydospores (thick-walled modified cells functioning as resting spores), and others.

• The cell of conidiophores producing conidia is called a conidiogenous cell and is produced either at the tip or the side of the conidiogenous cell, either single or in chains.

• The conidiophores are either free or aggregated to form specialized structures like Synnemata and Sporodochia. When they are large, the conidiophores are formed in specialized fruiting layers which are present within the specialized fruiting bodies called Conidiomata.

• There is a low sexual reproduction, but the parasexual cycle generally operates in their life to fulfil sexual requirements.

Deuteromycetes Fungi as Pathogens

There are thousands of Deuteromycetes species that are pathogenic to plants and plant parts. Many of these are responsible for the degradation of foods which include fruits and vegetables. All Deuteromycetes, like other types of fungi, are Heterotrophic and need to attach to an organic substrate. All major food products are the best substrates for fungi because, within a short period of time, the fungi will consume and destroy these fruits.

There are some fungi that are eligible to produce toxic chemicals harmful to those who like to eat rotting food. One such chemical is the aflatoxin, produced by the fungus Aspergillus flavus, and is majorly found on peanuts.

Deuteromycetes Classification

The Deuteromycetes is an artificial grouping in which the phylogenetic relationships among taxa are mostly unknown or not apparent. This classification comes under the mitotic states of meiotic groups such as basidiomycetes and especially the Ascomycetes. A small number of taxa has been correlated with meiotic states but the majority hasn’t.

There are different formal and informal names used in the past for groups of mitotic fungi. The most common are Deuteromycotina, Deuteromycetes, Fungi Imperfecti, asexual fungi, conidial fungi, and anamorphic fungi.

The Deuteromycetes classification is characterized by the absence of teleomorphic (meiotic) states. It is heterogeneous, i.e., polyphyletic. Reproduction occurs commonly by spores (conidia) produced mitotically (asexually) from conidiogenous cells.