Enrichment of gene functions in phage contigs
COG functions for all COG-annotated genes in HMP GI-tract-related bacteria were downloaded from the IMG/HMP site (http://www.hmpdacc-resources.org/cgi-bin/imgm_hmp/main.cgi) in December 2011. Frequency of each COG function in the bacterial set was compared with the frequency of the same function among all COG-annotated genes found in the pooled set of 991 phages. Only COGs appearing more than 10 times in the phage set were considered.