The duplicated MR/P fimbrial operons of M. morganii . The mrp operon (mrpABCDEFGHJ, solid red line region) is an important determinant of virulence in bacteria responsible for urinary tract infections. mrpI encodes a recombinase that controls the invertible promoter element of the mrp operon. A duplicated operon mrp' (mrpABCCDGEFE, broken orange line) is located immediately downstream of mrpJ. The numbers 292 through 314 represent the identifiers of M. morganii KT gene products MM0292 through MM0314. The term 'weak' denotes limited homology to the paralogous pair in mrp.