- The salCAB operon of Azospirillum irakense, required for growth on salicin, is repressed by SalR, a transcriptional regulator that belongs to the Lacl/GalR family. Somers, E., Keijers, V., Ptacek, D., Halvorsen Ottoy, M., Srinivasan, M., Vanderleyden, J., Faure, D. Mol. Gen. Genet. (2000)