Comparative gene cluster region (Region-1) organization. Genes denoted by the same color (except light yellow) are from the same orthologous group (top COG hit). Light yellow = no COG assignment. Figures 2-4 were generated at the IMG website as detailed in the Methods section (Additional file 1). The corresponding matching genomic positions were 1451145–1471145 for S. meliloti; 856122-8543524 for B. quintana; 760428–780428 for B. melitensis; 1745952–1758326 for R. etli; 3861924-3836924 for R. bellii; 1259027–1244027 for R. palustris; 180272–200272 for M. loti and 1936179–1931230 for A. tumefaciens. Between sec E and Ef-Tu proteins, the three plant symbiotic bacteria have a NDP-sugar epimerase protein (putative oxidoreductase protein; NP_385447 S. meliloti) which is absent in the other three bacteria. Further, only the Las strain has the tRNA-meth on the opposite strand, while other bacteria (B. quintana, B. melitensis, R. palustris, M. loti, S. meliloti) encode the tRNA/rRNA methyltransferase protein. This gene, however, was different from the cloned tRNA-meth (trm U) Las gene. On the other hand, there is a membrane protein coding gene (ter C) in A. tumefacians at that position. Similarly, none of the above bacterial species have the genes D-3-phosphoglycerate dehydrogenase and the phosphoserine aminotransferase in the gene cluster region that is present in Ca. Liberibacter asiaticus. The (//) indicates that this region is not yet cloned.