One of the most detailed genetic studies of any ecosystem to date has uncovered incredible biological diversity among subsurface bacteria. Researchers reconstructed the complete sets of genetic material, or genomes, of more than 2,500 microbes. The team took these microbes from sediment and groundwater samples collected from an area prone to flooding in Colorado. These genomes represent 80 percent of all known bacterial phyla. Analyses showed that interorganism interactions are required to turn the carbon, sulfur, and nitrogen cycles. Further, analyses revealed that complex patterns of community assembly are likely key to ecosystem functioning and resilience.