ABSTRACT
Growing populations and their greater longevity with widespread although not universal improvement in people's quality of life increase the worldwide demand for both more food and fresh water. This chapter discusses the interdependences that evolved between microorganisms and plants within emerging soil systems that gave rise to the plant microbiome. The diversified speciation of both plant and animal organisms has been made possible because in the world of microbes, there are reasonably easy and rapid exchanges of fragments of DNA that facilitate organisms' adaptation to new conditions. Microbial communities can adapt themselves to changing conditions by two means: by adding or eliminating certain species of bacteria or fungi and by transferring certain genes from one microorganism to another in a process known as horizontal gene transfer.
