Actinomycetes: a yet inexhaustive source of bioactive secondary metabolites

The rapid emergence of antimicrobial resistance among pathogens has led to a renewed interest to search for novel antimicrobial agents. The history of new drug discovery processes shows that novel skeletons have, in the majority of cases come from natural sources. This involves screening of microorganisms or plant extracts. They have been the source of, or inspiration for the development of chemical entities introduced as pharmaceutical. Among microorganisms, actinomycetes are enthralling resource due to their ability to produce novel bioactive secondary metabolites with antimicrobial activities. They have proven to be an inexhaustive mine of antimicrobial agents, especially those potent against pathogenic organisms. Microbial secondary metabolites, especially those from actinomycetes have been a phenomenal success for the discovery of novel drugs. They produce a wide range of secondary metabolites and more than 70% of the naturally derived antibiotics are currently in clinical use. They remain a fundamental source of new chemical diversity and an important part of drug discovery. Their ingenuity and immense industrial value is extremely noteworthy. The discovery of Streptomycin from actinomycetes has been imperative to the exploration of this group as a source of novel bioactive compounds. This group of organisms have produce antibiotics in different classes such as aminoglycosides, ansamycins, anthracyclines, glycopeptides, β-lactams, macrolides, nucleosides, peptides, polyenes, polyethers, and tetracyclines. Existence of actinomycetes has been reported in both terrestrial and marine habitats. This chapter highlight the bioactive metabolites produces by actinomycetes and their mode of action.