But when a plant harbors helpful microbes on its roots, it can fight off pests while maintaining normal growth. Of the amoebas, naked ones dominate soil. Soil fertility and physical and chemical composition of the soil determine the distribution of the microorganisms in the soil… For example, when a plant is fighting off a disease, its growth rate slows. Several types of microorganisms occur in soil. Examples of soil bacteria include rhizobium, azotobacter. Mostly ciliate and ameboid protozoa are present in the soil. These soil microbes … Also, they are motile and lack a cell wall. Soil microbes affect plants in an astounding way. Examples of aerobic bacteria include the Aerobacter genus which is widely distributed in the soil and actinomycetes bacteria genus Streptomyces which give soil … Most soil bacteria prefer well-oxygenated soils and are called aerobic bacteria and use the oxygen to decompose most carbon compounds. Microorganisms or microbes are organisms that are too small to be seen by the naked eye; they can only be seen under the microscope. These bacteria occupy the rhizosphere, a nutrient-rich habitat in the soil surrounding a plant's roots, and the phenazines act as a line of defense against pathogenic microbes, to prevent … Protozoa: These are microbes that have cells similar to animal cells. They like bacteria are spread in the soil.