Figure 4.

Heatmap of COG functional categories for genes with low position preference (10% lowest) for 328 microbial genomes compared to the genomic background. The color scale goes from -0.75 to 0.75 and represents the frequency of occurrences in each COG category among genes with low PP minus the overall frequency of occurrences in the genome. Over-represented categories among genes with lowest PP compared to the genomic background is indicated with purple, while green indicates under representation. For example, if all genes with low position preference corresponded to a certain COG category, and the same category only existed in 25 percent of all genes in that organism, the score would be 0.75 for that cog category for that organism. The kingdom is indicated as a vertical color bar to the left between the heatmap and the dendrogram. The phyla is illustrated as a vertical color bar to the right.