Metabolic Potential and Biotechnological Importance of Plant Associated Endophytic Actinobacteria

Abstract Actinobacteria, as a source of antibiotics, contribute to approximately two-thirds of known antibiotics. Endophytic actinobacteria colonize or reside inside the plant tissue without causing harmful effects to the host plant, and are present in almost every plant on earth. Invasion of endophytic actinobacteria takes place through the roots and spreads to other parts of the host plant. Endophytes promote plant growth by producing phytohormones, polymer degrading enzymes, and diverse secondary metabolites, as result of competition or antibiosis. Endophytic actinobacteria enhance plant growth indirectly by increasing the availability of nutrients, and through the induction of systemic resistance. They produce a broad range of structurally diverse secondary metabolites in association with medicinal plants through beneficial interactions or to withstand threshold levels inside the host under different climatic conditions. Bioactive metabolites produced from endophytic actinomycete may serve as a promising source to combat various phytopathogens, drug resistant clinical pathogens related to humans, and bioremediation in the environment. This chapter focuses on the metabolic potential of endophytic actinobacteria such as (1) Biocontrol agents against phytopathogens, (2) Antibacterial agents against human pathogens, (3) Bioremediation in the environment. The exploration of secondary metabolites from endophytic actinobacterial association with medicinal plants will provide further insight into plant endophyte interactions and enhanced level of fitness between the microorganisms and plants.