Abstract
Recent molecular phylogenetic analyses based on nucleotides directly obtained from environmental samples have indicated that the microbial diversity of naturally occurring microbial communities is much greater than previously assumed based on standard cultivation and isolation methods.Although the early investigations were conducted focusing on the identification and diversity of uncultivated bacterioplankton in oligotrophic ocean and coastal water environments, increasing attention has been paid to the phylogenetic diversity and ecological significance of uncultivated or unknown microorganisms belonging to the domains of Bacteria and Archaea in various environments.Extreme environments that were previously believed“abiotic”are now viewed as one of the most important targets for molecular exploration because these areas have turned out to harbor a great diversity of microorganisms, so-called“extremophiles”, having novel abilities and metabolisms that sustain them, while adapting to extraordinary conditions and that might provide great insights into understanding the origins of life and early evolution on primitive earth.Here, we present the short history of the molecular phylogenetic approach to naturally occurring microbial communities mainly in extreme environments introducing significant discoveries and findings.We also discuss improvement and new techniques for this approach, and the significant role played in future research.
