The study of microorganisms living in a variety of environments (air, soil, water, etc.) and their pathogenic relationship to other organisms including man.it includes (a) Microbial community genetics and evolutionary processes (b) element cycles and biogeochemical processes (c) Microbial life in extreme and unusual little-explored environments,(d)Structure and activities of microbial communities (e)Population biology of microorganisms etc. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information.