Bioactive Microbial Secondary Metabolites

Microorganisms have become a veritable resource of biologically active compounds. Thousands of such metabolites have been identified thus far and show a diversity of chemical structure, complexity, and physiological function. The types of bioactivity characterized have depended ultimately on the operational approach taken for their detection and isolation. Traditionally, the ability to antagonize the growth of bacteria, fungi, viruses, and other forms of life has been the major requirement. Therefore, it has resulted in the isolation of metabolites possessing mainly antibiotic activity. However, this trend is now being changed. It has become possible to design screening procedures that turn up active molecules having entirely different properties. The availability of powerful tools for increasing genetic variability, appreciation of the physiological characteristics of the producing organisms, as well as advances in biochemical understanding have been of enormous importance in developing new microbial strains for industrial application and basic research and in allowing microbial cells to be subverted for the purpose of making novel metabolites. However, the question of why microorganisms make all these metabolites remains unanswered. Little is known about the natural role of these important compounds. They have, therefore, been termed “secondary metabolites” so as to distinguish them from the primary metabolites of the cell that are known to be essential for growth of the organism.