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Actinobacteria and Environmental Adaptations
Actinobacteria are among the secondary metabolites producers and hold high pharmacological and commercial interest. It has great capability to produce secondary metabolites such as immunomodulators, antibiotics, anti-cancer drugs, growth factors, anthelminthic enzymes and herbicides.describes the historical isolation of bioactive compounds from Actinobacteria from the first isolation by Selman Waksman.
Global demand for new chemotherapeutic compounds and antibiotics with high bioactivity and low toxicity has increased recently due to the emergence of life-threatening microorganisms and multidrug resistance agents among viruses, bacteria and fungi . Additionally, the detection of secondary metabolites molecules with unique modes of action established various therapeutic agents’ strategies for treating many illnesses . To be more specific, endophytic Actinobacteria are microorganisms that represent a new production source of a large number of secondary metabolites, including alkaloids, beta-lactams, sulfonamides, aminoglycosides, glycopeptides, siderophores, quorum-sensing molecules, immunosuppressants, polyene macrolides, saccharides, pyrazoloisoquinolinones, butenolides, nucleosides and degradative enzymes . In fact, it has been reported that more than 10,000 various bioactive compounds have been discovered from Actinobacteria .
Endophytic microbes refer to a group of microorganisms, mostly fungi and bacteria, that exist in the host plant’s intracellular space. It usually causes no obvious harmful effect or symptoms of the disease and could produce various associations such as trophobiotic communalistic, mutualistic and symbiotic co-existence . Endophytes in woody plant hosts could exist within host tissues and protect host plants against herbivores and other pathogenic microorganisms . ActinobacteriaActinobacteria are Gram-positive bacteria with high guanine and cytosine (G + C) content in their genomes, and they are classified into 6 classes, 79 families of 46 orders and 10 fresh families of 16 new orders based on phylogeny using 16S rRNA sequences. The Actinobacterial classes consist of Thermoleophilia, Rubrobacteria Nitriliruptoria, Coriobacteria, Actinomycetia and Acidomicrobiia Salam et. al. . Actinobacteria have ubiquitous characteristics. They are present in diverse ecosystems on the earth such as endophytically with plants and in terrestrial and aquatic environments. An abundance of Actinobacteria species have been recorded in ordinary, extraordinary and extreme environments with high or low temperatures, high radiation, acidic/alkaline pH, salinity, low levels of available moisture and nutrients .
The genus Streptomyces is a Gram-positive bacteria. It is the largest genus of the phylum Actinobacteria, which has complex growth and can produce various secondary metabolites . In addition, there are more than 800 Streptomyces species that have been found to date (see http://www.bacterio.net/ Streptomyces .html (accessed on 20 August 2020) . Streptomyces is the major microbial genus of the most antibiotic-producing bacteria in the microbial world discovered so far, where streptomycin, gentamycin, rifamycin, chloramphenicol and erythromycin are produced by Streptomyces .
Actinobacteria have a large number of secondary metabolite biosynthetic gene clusters. Biosynthetic gene clusters (BGCs) are known as genes comprising locally clustered groups encoding a secondary metabolite biosynthetic pathway. In addition, BGCs contain genes encoding all enzymes required to produce secondary metabolites and pathway-specific regulatory genes. The Actinobacteria have diverse physiology and metabolic flexibility with high potential to produce novel bioactive compounds and enzyme production .
2. Mechanism of Bioactive Compounds from Actinobacteria against Drug-Resistant Pathogens
3. Conclusions and Future Prospects
The entry is from 10.3390/molecules26154504
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