Soil is an ecosystem capable of producing the resources necessary for the development of the living organisms. The characteristics of soil have great impact on the crops grown for sustaining this whole world. These characteristics are determined not only by physical and chemical but also biological properties including living flora and fauna. Millions of living organisms in soil make it’s living and dynamic system. These microbes undergo number of transformations, facilitating the availability of nutrients to the plants beside their role in the developments of soil. Soil microorganisms (bacteria and fungi) are responsible for biomass decomposition, biogenic element circulation, which makes nutrients available to plants, biodegradation of impurities, and maintenance of soil structure. But the activities of these organisms depend on soil factors either directly or indirectly. Soil microflora is very important constituent of organic matter present in the soil along with all other living and dead/decomposing materials. The soil living system, which supports all other organisms, begins with the soil bacteria and fungi. Bacteria are most abundantly found in the soil, while the fungus is present with great diversity of species. A number of bacteria and actinomycetes (aerobic and heterotrophic) species are responsible for decomposition of complex organic matters by participating in different nutrient cycles. pH, nutrient availability, temperature, water condition, and other factors all have an impact on N-fixing bacteria's and other microbes’ growth, survival, and metabolic activity. In other cases, environmental contamination has an independent effect on activity and metabolism of microbes. Water stress, salt stress, and other stressors can have an impact on the growth and activity of soil microflora.