Microorganisms occupy diverse habitats. They are found everywhere; in air, soil and water. Tremendous amount of research is directed towards studying their types, ecology, physiology, population and community structures. The present review aims at studying some interesting microbial examples present in the soil, their associations and ecological impacts. Attention is mainly directed towards the recent revelations on the role of Archaea, Mycorrhiza, methylobacteria, Azotobacter, Rhizobium and cyanobacteria in terrestrial environments.