Microbial Metabolites and Their Role to Improve Soil Health

Natural compounds secreted by microorganisms, known as microbial metabolites, are an essential component of the ecosystem and play an important role in agriculture and human welfare. Primary metabolites are important for microbial growth itself, including amino acids, nucleotides, vitamins, enzymes, organic acids, and alcohol. In contrast, microbial secondary metabolites, including antitumor agents, pigments, antibiotics, and growth hormones, are byproducts of microbial metabolism and are secreted near the stationary growth phase. These microbial products play an important part in a number of microbial metabolic processes such as biotransformation and the degradation of xenobiotic compounds. Some of them even act as plant growth-promoting factors (PGPBs). The soil contains a variety of microbiota that maximize crop yield by improving the soil’s health and fertility. Environmental sustainability is one among the three pillars of “One Health” concept and is directly impacted by soil health. Soil microbiota execute fundamental soil processes such as biomass decomposition, nutrient cycling, stimulating plant growth, and higher crop yields. However, the microbial flora, soil structure, and dynamics are significantly influenced by the physicochemical features of the soil, such as the quality of its organic content, biomass density, pH, redox potential, etc. This chapter focuses mainly on the diverse soil microbiota, their metabolic products, and their contribution in improving soil health. The reader will receive comprehensive information on soil health indicators, the characteristics of healthy soil, and how microbial metabolites, e.g., extra-polymeric substances or exopolysaccharides, siderophores, microbial enzymes, phytohormones, and antagonistic molecules, contribute to the soil’s good physical and chemical properties.