A metaBiome consists of all the microorganisms (bacteria, single-cell eukaryotes and viruses) that are living on or in the human body or other environments. 400 to 1000 species of bacteria populate the human gut, most harmless or beneficial to the host by providing essential nutrients such as short-chain fatty acids, B vitamins and vitamin K. The composition metabiome is influenced by many factors, including age, genetic background, diet and other environmental exposure. Disruption of the homeostatic metabiome can result in disease, and has also been implicated in social behavior, reproduction, growth and cognition. It is estimated that with bacterial protein-coding genes nearly 400 times more abundant than human genes, which might suggest microbes contribute more genes responsible for human survival than humans’ own genes.
Bacterial metabiome sequencing is accomplished by amplifying the 16S rRNA V3 and V4 region. The resulting amplicons are used to prepare a sequencing library and the data is analyzed against the Greengenes database. The result is a breakdown of the sample composition, with classification at several taxonomic levels.