Fig. 1

Overall scheme of the predicted cys regulon genes from Escherichia coli and putative orthologs identified in X. citri genome. (a) cys regulon genes from E. coli and (b) orthologs found in X. citri. Green boxes indicate the genes for the sulfate (SO₄ ^2-) uptake system that are responsible for binding and reduction to sulfide, through a set of reactions whose intermediates are adenosine-5’-phosphosulfate (APS), 3’-phosphoadenosine-5’-phosphosulfate (PAPS) and sulfite. Identical colored lines (red, green and black) in boxes from X. citri genes represent genes that belong to the same predicted operon. CysP, only identified in E. coli, is the periplasmic component for thiosulfate uptake that uses the same sulfate transporter. Light blue boxes indicate the genes that are described for the transport and assimilation of alkanesulfonates. Based on the sequence identity and molecular modeling, the taurine transporter and TauD of the E. coli pathway (shown in gray) were not identified in X. citri, but seem to be replaced by other homologs of putative alkanesulfonate or aliphatic sulfonate transporter and desulfonative enzymes (SsuD1 and SlfA) (darker blue boxes). The red boxes show the regulatory genes, cysB, cbl. All genes are identified by their KEGG code and when present, the name of the putative protein. P: periplasmic space, I.M.: inner membrane, C: cytoplasm