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Allelic Variation within Helicobacter pylori babA and babB
D T Pride1, R J Meinersmann, M J Blaser
1Division of Infectious Diseases, Department of Medicine, Vanderbilt University School of Medicine and VA Medical Center, Nashville, Tennessee, USA. David.T.Pride@Vanderbilt.edu
Infection and Immunity
|February 13, 2001
Summary
Helicobacter pylori outer membrane protein genes babA and babB show geographic variation and independent evolution. Allelic diversity exists, but does not determine Lewis B binding in these H. pylori strains.
Area of Science:
- Microbiology
- Genetics
- Evolutionary Biology
Background:
- Helicobacter pylori exhibits geographic and disease-specific variations in its genetic makeup.
- Outer membrane proteins, such as babA and babB, play crucial roles in bacterial interactions and virulence.
- Understanding the diversity of these genes is key to deciphering H. pylori's adaptability and pathogenic potential.
Purpose of the Study:
- To investigate the allelic diversity within the babA and babB genes of Helicobacter pylori.
- To determine the evolutionary relationships and geographic distribution of babA and babB alleles.
- To assess the influence of babA and babB allelic variation on Lewis B binding.
Main Methods:
- Analysis of the central regions of babA and babB genes in 42 H. pylori strains from diverse geographic locations.
- Phylogenetic analysis to determine allelic groupings and evolutionary relationships.
- Examination of synonymous and nonsynonymous substitutions to infer evolutionary rates and constraints.
- Assessment of recombination patterns and their impact on genetic diversity.
Main Results:
- Five distinct allele groups of babA (AD1-AD5) and three of babB (BD1-BD3) were identified.
- Phylogenetic analysis revealed independent evolution of babA and babB alleles, with significant geographic variation.
- babA exhibits higher diversity than babB, suggesting an earlier evolutionary origin for its diversity region, potentially with stronger functional constraints.
- Recombination is a significant factor in the evolution of both genes, but clonal descent remains evident.
- Neither babA nor babB allelic variations were found to be determinants of Lewis B binding in H. pylori.
Conclusions:
- The babA and babB genes in H. pylori display substantial independent allelic and geographic variation.
- Evolutionary pressures, including recombination and functional constraints, shape the diversity of these outer membrane protein genes.
- Despite their role in host interactions, specific allelic variations in babA and babB do not dictate Lewis B antigen binding by H. pylori.