Microbial Secondary Metabolites and Defense of Plant Stress

Abstract Microbial secondary metabolites are low-molecular-weight bioactive compounds produced during the late growth phase of microorganisms. They are functionally diverse and show a variety of biological activities such as antimicrobial, plant growth stimulator, insecticidal, and herbicidal activities. Secondary metabolites including terpenes, phenolics, and nitrogen-containing compounds defend plants against biotic and abiotic stresses. This chapter presents an overview about the different types of secondary metabolites produced by microorganisms and their role in plant defense against different stresses.