MOLECULAR ANALYSIS OF UREASE GENES FROM A NEWLY IDENTIFIED UNCULTUREDSPECIES OF HELICOBACTER

''Gastrospirillum hominis'' is an uncultured gastric spiral bacterium that has recently been shown by 16S rDNA sequence analysis to be a new ly recognized species of Helicobacter that infects humans, and it has been provisionally designated ''Helicobacter heilmannii.'' We used PCR to directly amplify the urease structural genes of ''H. heilmannii'' from infected gastric tissue. DNA sequence analysis identified two ope n reading frames, ureA and ureB, which code for polypeptides,vith pred icted molecular weights of 25,729 and 61,831, respectively. The urease subunit genes from ''H. heilmannii'' were cloned and expressed in Esc herichia coli. Western blot (immunoblot) analysis showed that antiseru m directed against the ureA and ureB gene products from H. pylori was cross-reactive with the corresponding polypeptides from ''H. heilmanni i.'' Analysis of the derived amino acid sequences of ''H. heilmannii'' UreA and UreB demonstrated that ''H. heilmannii'' urease is more high ly related to the urease from H. felis (found in the stomachs of cats and dogs) than to the urease from H. pylori. These data are consistent with 16S rDNA sequence analysis and suggest that ''H. heilmannii'' is phylogenetically most closely related to H. felis.