Actinomycetes

Background

Actinomycetes is a nontaxonomic term for a group of common soil microorganisms sometimes called "thread or ray bacteria." Actinomycetes are a versatile group of Gram-positive, rod shaped and spore forming bacteria widely distributed in the terrestrial and aquatic environments [6]. These are prokaryotic organisms that are classified as bacteria, but are unique enough to be discussed as an individual group [7]. The specialty of the actinomycetes is that they have a mycelial appearance unlike most bacteria. These bacteria are rather unexplored because the cultivation and maintenance of actinobacteria are not that easy as in the case of other bacteria. They are an important component of the bacterial communities, especially under conditions of high pH, high temperature or water stress. Although they were originally recognized as soil microorganisms, it is now being recognized that marine actinomycetes are also important. Actinomycetes are heterotrophic in nature. Most of them are strict saprophytes, while some from parasitic or mutualistic associations with plants and animals [1].

Distribution & Ecology

Actinomycetes can be found in a wide range soil and marine habitats in different parts of the world. Because they can live in different environments and exhibit high versatility in their nutrition, this allows them to spread and thrive in different regions across the globe and compete with other organisms in their surroundings. While Actinomycetes can be found in a variety of habitats, they constitute a huge extent of the microbial population in many soils. Thus making them some of the most common micro-organisms in different types of soil (about 1 million cells per gram of soil). However, a variety of factors like pH, oxygen, and temperature influence the species that inhabit different types of soil [3]. It has been found that the pH is a major environmental factor determining the distribution and activity of soil actinomycetes as Neutrophils' occur in less number in acidic soils below pH 5.0, whereas acdophilic and acidoduric streptomycetes are more numerous in acidic soils [1]. The biggest groupings of actinomycetes in the soil can be found in the organic horizon. Actinomycetes may assume a part in advancing plant development, through control of root pathogens or in some aberrant route, since a few species can produce antifungal compounds [4]. It is also important to note that there is evidence that actinomycetes usually form a small fraction of the bacterial flora in marine habitats, but population numbers are lower compared with those from terrestrial and freshwater sites.

Significance

Actinomycetes play an key role in the break down of various organic materials in soil as well as their ability to produce a range of bioactive molecules, including antibiotics and various kinds of enzymes. Their role in the decomposition of plant and other material especially in the degradation of complex and relatively recalcitrant polymers is hugely important. Lignin, cellulose and lignocellulose are all examples of what they degrade. There is evidence that actinomycetes are involved in the degradation of many other naturally occurring polymers in soil such as hemicellulose, pectin, keratin, chitin and fungal cell wall material [1]. Given that they help recycle materials that can be used by plants, it is beneficial in agriculture practices. They also produce a variety of enzymes that are useful in various industries, such as the medical industry. As they are known for their ability to produce various antibiotics, the actinomycetes are widely explored by various research groups in search of novel drug molecules. Another significance of these bacteria is that from the rhizosphere, they suppress the growth of pathogens. Since they produce various bioactive metabolites that are used to produce various drugs (antifungal, anti-parasitic and antibiotics etc).

References

• [1] C. Dilip V., Mulaje S. S., Mohalkar R.Y. 2013, May. A REVIEW ON ACTINOMYCETES AND THEIR BIOTECHNOLOGICAL APPLICATION | International Journal Of Pharmaceutical Sciences And Research.

• [2] A Closer Look at Actinomycetes – Nova Science Publishers. 2020, April. . https://novapublishers.com/shop/a-closer-look-at-actinomycetes/.

• [3] Actinomycetes - Definition, Classification/Characteristics and Culture. (n.d.). https://www.microscopemaster.com/actinomycetes.html.

• [4] Ali Mohammed Abdullah Bawazir, Manjula Shantaram. (n.d.). Ecology and distribution of actinomycetes in nature– A review. http://journalcra.com/article/ecology-and-distribution-actinomycetes-nature%E2%80%93-review.

• [5] Bawazir, A. M. A., M. Shantaram. 2018. ECOLOGY AND DISTRIBUTION OF ACTINOMYCETES IN NATURE– A REVIEW. International Journal of Current Research 10:5.

• [6] Loynachan, T. 2008, June 4. Soil Actinomycetes. Text. https://www.asmscience.org/content/education/imagegallery/image.3180.

• [7] Pepper, I. L., and T. J. Gentry. 2015, December. Actinomycete - an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/actinomycete.