Structures of gene clusters for protocatechuate catabolism. Homologous genes are shaded in the same way. Arrows with dotted borderlines represent Rhodococcus genes for which no or only partial sequence information is available. The information was compiled from the following sources: P. putida, references 7, 19, 27, 32, 49, 57, and 71; A. calcoaceticus, references 20 (U04359), 24, 25, and 36; A. tumefaciens, references 51 and 52.