Comparison of xylose operon and phosphonate operons. (a) Insertion of Genomic island 8 (Bp-GI 8) and deletion of xylose operon (red) in Bp. The xylose utilization operon in Bt is absent in Bp, being replaced by Bp-GI 8. (b) A phosphonate gene cluster (pink) is present in Bp while absent in Bt. Genes in purple represent orthologous proteins. See Main Text for details.