Cell lysis is responsible for the appearance of extracellular urease in Helicobacter pylori

Background. Helicobacter pylori is a neutralophilic bacterium that colonize s the acidic human gastric surface using the neutralizing capacity of a con stitutively produced urease. Urease is present both in the cytoplasm and bo und to the outside surface of the bacteria. The origin of the surface ureas e continues to be controversial. This study provides additional evidence th at the origin of surface urease is cell lysis, not secretion. Methods. H. Pylori was transformed with a plasmid encoding green fluorescen t protein (GFP), a non-native cytoplasmic protein. Cultures supplemented wi th beta -cyclodextrin or horse serum were collected over various time perio ds and spun through a ficoll cushion to gently separate whole bacteria from released protein. The pellet and supernatant fractions were analyzed by fl uorimetry, SDS-PAGE and Coomassie blue or Western analysis. Results. GFP fluorescence and antigenic reactivity in the supernatant incre ased at each time point. GFP, the non-native cytoplasmic protein, and UreB, a native cytoplasmic protein, increased over time in the supernatant and b oth proteins were always present in the pellet fraction. UreI, an inner mem brane protein, was only present in the pellet fraction. beta -galactosidase , a protein not found in H. pylori, was used as a negative control. Conclusions. Since it is unlikely that there is an intrinsic secretion syst em for GFP, a non-native protein, its increasing presence over time in the supernate fraction along with UreB, and retention of UreI in the pellet fra ction implies that cell lysis accounts for the presence of urease on the su rface of H. pylori.