8 - Endophytic bacteria for drug discovery and bioremediation of heavy metals

Abstract

Endophytic bacteria are the bacteria that reside asymptomatically in the tissues of higher plants and can improve plant growth under biotic and abiotic stressors by stimulating immune responses, excluding plant pathogens, improving plant nutrient uptake and by modulating growth and stress-related phytohormones. The endophytes act as reservoirs of novel bioactive secondary metabolites, such as alkaloids, phenolic acids, quinones, steroids, saponins, tannins, and terpenoids that serve as a potential candidate for modern medicine, agriculture, and industry. These bioactive compounds exhibiting a variety of biological activities such as antimicrobial, anti-insect, anticancer, antimycotics, immunosuppressants, antioxidant compounds, and anticancer compounds. Similarly, actinobacteria class endophytes are responsible to synthesize metabolites that have antimicrobial and antitumor-like activity. These metabolites are used in agriculture, medical, and veterinary field. The drug resistance in bacteria, the appearance of life-threatening viruses, the fungal infections, the recurring problems with disease in persons with organ transplants, among the world's population increases the need for developing the novel drugs that can cope with the recurring problems of world. These novel endophytic bioactive compounds may act as the solution for these problems. Structure elucidation of the isolated chemicals and characterization of their biosynthetic pathways provides a basis for these novel compounds to be investigated in clinical trials and for commercial purposes. Bioremediation is an eco-friendly and efficient method a used to remove environmental contaminants from the ecosystem by making use of the biological mechanisms inherent in microbes and plants to eradicate hazardous pollutants and restore the ecosystem to its original condition. Among bacteria, Methylobacterium spp., as well as the representatives of Gram-positive bacteria, is the most widespread bacterial species that helps in bioremediation. In this chapter we are interested to discuss the role of endophytic bacteria in drug discovery and bioremediation aspects of heavy metals.