Fig. S4. Clusters of orthologous groups (COGs) of differentially expressed genes. The numbers correspond to the groups as defined in Figure S3. Asterisks mark significantly over-represented COGs (p-value < 0.05) in the groups of differentially expressed genes as identified by broken-stick analysis performed in R. Information on COGs has been downloaded from the integrated microbial genomes database (http://img.jgi.doe.gov/cgi-bin/w/main.cgi).