Subsystems present in different metagenome sequences. The subsystems present in the Soudan samples, the Iron Mountain AMD sample, the Minnesota Farm and the Sargasso Sea are shown grouped by family. The red x corresponds to very low abundance or complete absence of that family of subsystems. The size of the circle represents the proportion of sequences seen within that family of subsystems.
Edwards et al. BMC Genomics 2006 7:57 doi:10.1186/1471-2164-7-57