This document summarizes a study that analyzed changes in bacterial and archaeal communities during thermophilic composting of cattle manure using PhyloChip microarray technology. Samples were collected from different areas of a compost pile based on age and temperature. Total DNA was extracted from the samples and the 16S rRNA gene was amplified and hybridized to a PhyloChip array. Statistical analysis showed differences in microbial populations between raw manure samples and compost samples. During composting, archaeal phyla Thaumarchaeota and Thermoprotei and bacterial phyla Actinobacteria and Firmicutes increased in diversity. Ammonia-oxidizing and methanogenic microbes increased under thermophilic conditions. The