BRADYRHIZOBIUM-JAPONICUM FIXK(2), A CRUCIAL DISTRIBUTOR IN THE FIXLJ-DEPENDENT REGULATORY CASCADE FOR CONTROL OF GENES INDUCIBLE BY LOW-OXYGEN LEVELS

Bradyrhizobium japonicum possesses a second fixK-like gene, fixK(2), i n addition to the previously identified fixK(1) gene, The expression o f both genes depends in a hierarchical fashion on the low-oxygen-respo nsive two-component regulatory system FixLJ, whereby FixJ first activa tes fixK(2), whose product then activates fixK(1). While the target ge nes for control by FixK(1) are unknown, there is evidence for activati on of the fixNOQP, fixGHIS, and rpoN(1) genes and some heme biosynthes is and nitrate respiration genes by FixK(2), FixK(2) also regulates it s own structural gene, directly or indirectly, in a negative way.