Distribution of Protein BLAST scores (−log(E-value)) for various sets of E. coli genes scored against genes in the B. subtilis genome. At the top, in cyan, is the distribution of the best-match BLAST scores for each of the 4145 genes in the E. coli genome. 1461 of these are also reciprocal best hits of the B. subtilis genome against E. coli; the distribution of these scores is shown in dark blue. 746 distinct pairs of E. coli – B. subtilis genes are connected by one or more 10-mer matches; the distribution of BLAST scores for these matches is shown in red. In magenta is shown the distribution of BLAST scores for the 388 genes that are both reciprocal BLAST best hits and connected by one or more 10-mers. At the bottom of the plot, in green, is the distribution for genes with matching 10-mers and the word ‘transporter’ in either gene’s annotation. The peak at the right of the plot indicates the 37 pairs of genes given an E-value of ‘0.0’ by BLAST.