The microbial world is ubiquitous, abundant, adaptable, and dynamic, which can be found in every environmental on Earth ranging from deep ocean, polar ice, desert, root of plants, soil to inside of human body (Schaechter et al 2005). As the first cellular of life forms, the microbes can be used to determine when life has existed on Earth (Schaechter et al 2005; Waggoner & Speer 1998). Being the former of life, microbes have had a very long time to evolve and develop the basic metabolic mechanisms that made all other life possible and occupy a great variety of ecological. Moreover, microbes have also being an essential part in biogeochemical cycle which is a key element for making Earth habitable (Schaechter et al …show more content…
Those of first three kingdoms contain multi-celled organisms, animals, plants and fungi. Otherwise, two other kingdoms, bacteria and protists are categorised mostly as single-celled organism (but some are multi-celled species).
Recently, there is a new tree family revealed by recent research and made up two main divisions that are the Prokaryotae and the Eukaryotae (Woese et al 1990; Waggoner & Speer 1998) The Prokaryotae consist of two domains, the Archaea and the Bacteria, and have one kingdom of each domain. Meanwhile the Eukaryotae have only one domain, Eukaryota or eukaryotes, and was divided into four kingdoms that are animals, plants, fungi and protists. Figure 1 is shown the three domain of life