Extremophiles: A promising source of novel natural products

Extremophiles, the microorganisms inhabiting different extreme environments char-acterized by high or low temperature, high or low pH, high salt concentration, high pressure, high radiation, etc. or combinations thereof, have developed unique strate-gies for adapting and thriving in such environments. Studies on extremophiles have been pursued with great interest to determine the mechanisms of adaptation and also as an important source of useful products including enzymes, polymers, com-patible solutes, etc. During the last 20–30 years, attention has been directed toward search for novel bioactive compounds produced by extremophiles, which most likely are playing a role in controlling microbial population in the respective ecological niches and are also promising candidates for applications in foods and healthcare. Secondary metabolites produced by microbes have long been a major source of natural products for drug development. Toward the end of the last century, however, high rates of rediscovery of bioactive products from nature prompted a shift to high-throughput screening programs based on molecular targets and combinatorial chemistry, which has unfortunately not led to major discoveries of novel products, and the trend is now to build focused libraries around the chemical scaffolds of natural products. An urgent need for new molecules that could potentially replace the present-day antibiotics, which are becoming ineffective due to the resistance devel-oped by the pathogens, has served as an important driver for the increasing efforts on mining the unexplored ecological niches for bioactive compounds.