H. pylori colonizes a hostile gastric environment where few other organisms can survive. Its prolonged presence in this milieu is associated with gastric diseases such as gastritis, ulcers, and gastric cancer (, , –60). One of the basic features that may aid the bacterium to colonize this niche is a unique PG with a low level of cross-linking, short glycan chain length, and lack of trimers and tetramers. These features suggest that the murein of H. pylori is loosely constructed, and thus readily susceptible to alterations enabling the organism to change its morphology according to environmental needs and, in particular, to the process of colonizing new subjects.
Analysis of the H. pylori genome shows the presence of genes coding for all the enzymes of the biosynthetic pathway leading to the disaccharide pentapeptide, which is the basic building block of murein. Also identified are genes encoding the putative murein synthases PBP1, PBP2, and PBP3, which exhibit strong sequence similarities to penicillin-binding proteins encoding transglycosylase and transpeptidase domains from other bacteria, including E. coli, Haemophilus influenzae, and Bacillus subtilis, and which are involved in the construction of the murein sacculus, maintenance of cell shape, and cell division. There is some experimental evidence that indeed these are their functions in H. pylori.
Regarding murein hydrolases required for murein turnover and recycling, as well as for cell proliferation, the data obtained from genome analysis are much more fragmentary. Only a few ortholog genes to those present in other bacteria have been found, and their functions in H. pylori remain to be characterized.
Several other proteins able to bind labeled β-lactams have been detected in H. pylori, but nothing is known yet about their identity and further studies are required to understand the function of these putative PBPs.
Copyright © 2001, ASM Press.