Figure 4.

Detail of part of Figure 3, showing a chromosomal island. The island extends from 855 to 908 kilobases, genes RL0790-RL0841, and is recognizable by low GC3s (G+C content of silent third positions of codons) and absence of quartop genes. RA-SM denotes the tree that pairs R. leguminosarum with A. tumefaciens, and S. meliloti with M. loti; RM-AS and RS-AM are similarly defined.