Overview: Actinomycetes

Sometime during our studies we come across many terms and words which we do not remember or we are not familiar with. In that situation either we consult a dictionary or google the word. So I thought about to make a series which give general overview of microbiology related terms. I am trying to provide as much as possible.

So today the word is Actinomycetes.

Definition

Actinomycetes also called as Actinobacteria are unicellular, gram positive, rod shaped, spore forming, and facultative anaerobic bacteria. They don’t have true cell wall like bacteria and can produce mycelium like fungi and because of this noted ability, actinomycetes also known as connected link between bacteria and fungi.

Discovery

The term actinomycetes means “ray fungus” in Greek. It is first discovered by Ferdinand Cohn in 1875 from human lacrimal duct and named it Streptothrix foersteri. In 1878, C.O. Harz named an organism that he isolated from a case of bovine lumpy jaw, as Actinomyces bovis.

Presence

Actinomycetes are widely distributed in both terrestrial and aquatic ecosystems. They can be present as spore or vegetative form in soil, aquatic bodies, compost, plant litter, and food products. Actinomycetes also present in human, animals and plants.

Reproduction

Actinomycetes reproduced by two ways; spore formation and hyphae fragmentation. During reproduction, Actinomycetes can form conidiophores, oidiospores and sporangiospores. In reproducing through hyphae fragmentation, the hyphae formed by Actinomycetes are smaller than fungal hyphae, and bear long spore chains.

Importance

Actinomycetes decompose complex mixtures of polymers in dead plants, animals and fungal materials such as chitin, lignin, keratin and cellulose. This process produces several volatile substances like geosmin, responsible for distinctive earthy odour and lead to a humus formation which make the soil fertile.

Actinomycetes are most abundant in soil and play a major role in nitrogen fixation by having symbiotic relationship with plants.

Actinomycetes metabolic products are helpful for human being as those can be used as various purposes e.g. antibiotics (erythromycin, tetracycline etc.) pigments, enzyme inhibitors, and biotechnologically relevant enzymes (catalase, protease etc.).

Actinomycetes not only play a beneficial role but also can be pathogenic to plants, animals, and man. Plant diseases like rot of sweet potato and human diseases such as tuberculosis, paratuberculosis, mycetomas, actinomycosis, allergic pneumonias, and various types of abscesses are caused by actinomycetes.


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