With recent advances in gene sequencing technology, it has become possible to sequence the genetic material of entire microbial communities, such as all microbes present in a sea water sample, or in the human gut. While the specific microbes
present in the sample may vary rapidly over time, the dominant biological functions performed by the entire community may be
stable and scientifically significant. In a 2006 paper, Dinsdale et al investigated metagenomes from a variety of environments and found that they could separate the samples according to environment by looking only at the dominant genes present. We expanded this study to a much larger set of metagenomes, using more statistical techniques, and came to the same conclusion: while species vary widely, there is a close connection between environment and the biological functions performed by the microbial community that lives in that environment.