ABSTRACT
A small amount of environmental sample, such as a handful of soil, is rich in microbial life, but the number of microbial species in such a sample is unknown. The microbiome on or within our body contains tens of thousands, if not more, species of bacteria, fungi, and archaea. Besides their tremendous species diversity, the composition, as well as function, of such microbial communities is not static but constantly changing according to the status of their environment. Our current understanding of these diverse and dynamic microbial communities is still significantly lacking, as most of our knowledge comes from culturable species. For those that still cannot be cultured in the lab, which comprise the majority of microorganisms on earth, we know very little. Metagenomics offers an important approach to study microbial diversity in these environmental communities without relying on artificial culturing. Also referred to as environmental or community genomics, metagenomics examines all genomes existing in a microbial community as a whole without the need to capture or amplify individual genomes. Through simultaneous analysis of all DNA molecules present in a microbial community, metagenomics provides a profile of taxonomic composition and functional status of the community and its environment.
