|Meinersmann, Richard - Rick|
Submitted to: Journal of Infectious Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/5/2001
Publication Date: 7/1/2001
Citation: NACHAMKIN, I., ENGBERG, J., GUTACKER, M., MEINERSMANN, R.J., LI, C.Y., ARZATE, P., HO, T.W., ASBURY, A.K., GRIFFIN, J.W., MCKHANN, G.M. POPULATION BIOLOGY OF CAMPYLOBACTER JEJUNI O:19 ASSOCIATED WITH GULLAIN- BARRE SYNDROME AND GASTROENTERITIS. JOURNAL OF INFECTIOUS DISEASES. 2001. Interpretive Summary: Helicobacter pylori is the species of bacteria that colonizes the human stomach and causes stomach ulcers. The organism is considered to be closely related to Campylobacter, a group of organisms that cause diarrheal disease and are often found on poultry products. Both Helicobacter and Campylobacter show a great amount of variation from one culture to the next and, perhaps, understanding how one organism generates diversity may help to show how the other organism becomes more diverse. This was a study of two genes, babA and babB, coding for proteins found on the surface of Helicobacter. The proteins are similar to each other and it was thought that the evolutionary route taken by each gene might also be similar. This turned out not to be the case, each gene evolved in patterns that indicated different histories. This is characteristic of genes that are shared by DNA transfer between different strains in a process known as recombination. Other evidence indicates that such sharing of the two genes was likely. However, each gene showed correlation with the geographic location from which the strain of bacteria was recovered. This can only occur if gene mutations occur faster than the exchange of DNA. Thus, Helicobacter show rapid rates of genetic exchange and rapid rates of mutation of the babA and babB genes. However, the character of these genes did not correlate with known pathogenicity traits for H. pylori.
Technical Abstract: Helicobacter pylori strains show both geographic and disease-associated allelic variation. We investigated the diversity present in 2 genes, babA and babB, which are members of a paralogous family of outer membrane proteins. Eleven family members within a single H. pylori strain, predicted to encode proteins with substantial and C-terminal similarity to each other, were classified as babA paralogues. In their central regions, most are less than 54% related to one another. Examining the babA and babB central regions in 42 H. pylori strains from different geographic locales, we identified five different allele groups of babA (AD1-AD5), and three different allele groups (BD1-BD3) of babB. Phylogenetic analysis revealed that the allelic groupings of babA and babB are independent of one another, and that for both, geographic variation is present. Analysis of synonymous and nonsynonymous substitutions in these regions showed that babA is more diverse, implying an earlier origin than the same region of babB, but that the babA diversity region may have more functional constraints. Although recombination has been central to the evolution of both genes, with babA and babB showing low mean compatibility scores, and homoplasy ratios of 0.71 and 0.67, respectively, recombination is not sufficient to obscure evidence of clonal descent. Despite the involvement of babA in binding to the host blood group antigen Lewis B, neither the presence of different babA nor babB allele groups are determining factors in Lewis B binding of H. pylori strains.