ORGANIZATION OF UREAPLASMA-UREALYTICUM UREASE GENE-CLUSTER AND EXPRESSION IN A SUPPRESSOR STRAIN OF ESCHERICHIA-COLI

Ureaplasma urealyticum is a pathogenic ureolytic mollicute which colon izes the urogenital tracts of humans. A genetic polymorphism between t he two biotypes of U. urealyticum at the level of the urease genes was found. The urease gene cluster from a biotype 1 representative of U. urealyticum (serotype 1) was cloned and sequenced. Seven genes were fo und, with ureA, ureB, and ureC encoding the structural subunits and ur eE, ureF, ureG, and a truncated ureD gene encoding accessory proteins. Urease expression was not obtained when the plasmid containing these genes was incorporated into an opal suppressor strain of Escherichia c oli, although this enzymatic activity was found in the same E. coli st rain transformed with pC6b, a plasmid with previously cloned urease ge nes from the U. urealyticum T960 strain of biotype 2 (serotype 8). Alt hough there are 12 TGA triplets encoding tryptophan within urease gene s, the level of expression obtained was comparable to the levels repor ted for other bacterial genes expressed in E. coli. Nested deletion ex periments allowed us to demonstrate that ureD is necessary for urease activity whereas another open reading frame located downstream is not. The promoter for ureA and possibly other urease genes was identified for both serotypes.