Actinomycetes

(From Science Direct)

Actinomycetes are prokaryotic organisms that are classified as bacteria, but are unique enough to be discussed as an individual group. Actinomycete numbers are generally one to two orders of magnitude smaller than the total bacterial population. They are an important component of the bacterial community, especially under conditions of high pH, high temperature or water stress. Morphologically, actinomycetes resemble fungi because of their elongated cells that branch into filaments or hyphae. These hyphae can be distinguished from fungal hyphae on the basis of size with actinomycete hyphae much smaller than fungal hyphae.

One distinguishing feature of this group of bacteria is that they are able to utilize a great variety of substrates found in soil, especially some of the less degradable insect and plant polymers such as chitin, cellulose and hemicellulose.

Although originally recognized as soil microorganisms, it is now being recognized that marine actinomycetes are also important. Specifically, marine actinomycetes have been shown to possess novel secondary metabolites that add a new dimension to microbial natural products that have been discovered within soil actinomycetes.

Actinomycetes have gained interest in agroindustry as a source of biologically active compounds, biocontrol agents, and PGPRs. Within actinomycetes, Streptomyces is the most used. According to Tanaka and Omura (1993), about 60% of the new insecticides and herbicides originated from these microorganisms. This growing interest is due to their low toxicity and environmental friendliness; they have a degradable nature while being highly specific and less toxic to nontarget organisms. However, the identification of novel species as well as the mechanism of action of these bioagents is needed for the development of actinomycete-based products commercially available with a prolonged shelf life.