Chemotactic response of Helicobacter pylori to human plasma and bile

To clarify further the role of chemotaxis in Helicobacter pylori colonization, the in vitro bacterium response to human plasma and bile (secretions containing chemoeffector compounds that are present in the gastric mucus layer) was examined. Human plasma, after dilution to 1 % (v/v) with buffer, was found to be a chemoattractant for the motile bacillus. Human gall-bladder bile, after dilution to 2 % (v/v) with buffer, was found to be a chemorepellent, but did not cause the motility of the bacillus to be diminished after prolonged exposure. The basis of the chemoattractant effect of plasma was explored by examining how urea. and 12 amino acids found in plasma affected the taxis of H. pylori. Urea and the amino acids histidine, glutamine, glycine and arginine were the strongest chemoattractants. Other amino acids were chemoattractants, with the exceptions of aspartic and glutamic acids, which were chemorepellents. The basis of the chemorepellent effect of bile was explored by examining how the six most abundant conjugated bile acids in human bile affected the taxis of H. pylori. All the bile acids were chemorepellents, with the greatest effects being demonstrated by taurocholic and taurodeoxycholic acids. The implications of these findings for H. pylori colonization of gastric epithelium are discussed.