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United States Department of Agriculture

Agricultural Research Service

Title: H.PYLORI Rnr Homologue (Hp1248) Demonstrates Star Phylogeny

Authors
item Meinersmann, Richard
item Romero, J - VANDERBILT UNIVERSITY
item Blaser, M - VANDERBILT UNIVERSITY

Submitted to: Campylobacter Helicobacter and Related Organisms International Workshop
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 1999
Publication Date: September 12, 1999
Citation: MEINERSMANN, R.J., ROMERO, J., BLASER, M.J. H.PYLORI RNR HOMOLOGUE (HP1248) DEMONSTRATES STAR PHYLOGENY. CAMPYLOBACTER HELICOBACTER AND RELATED ORGANISMS INTERNATIONAL WORKSHOP. 1999.

Technical Abstract: RAPD was used to examine H. pylori populations. A patient was identified in whom isolates from antrum and cardia biopsies yielded an extra band not found in isolates from the fundus biopsy. Sequence analysis showed this band was part of HP1248 (rnr-homologue). Additional polymorphisms were found in rnr amongst these strains, but the flanking HP1247 & HP1249 as well as the recA & glmM genes showed no polymorphisms. Analysis of the complete sequence of HP1248 from 5 strains showed an average base difference of 5.58 percent, with 226 polymorphic sites, 73 of which were informative. Linkage could be shown for few of the informative sites, but statistical tests could not document any recombination sites. The mean KA/KS was 0.37. Tests for selection were unable to support the neutral hypothesis. We then examined 57 H. pylori strains & analyzed sequence polymorphisms for a 231 bp 5'region & a 126 bp 3'region. Neighbor-joining analysis of distances yielded a star phylogeny for both fragments. For the 5'fragment, KA/KS = 0.12, & for the 3'fragment = 0.40,indicating the possibility of differential selection for these two regions of a single gene. In the 5'region, there is an 18 bp island of linkage disequilibrium, & nearly all other informative poylmorphic sites were not linked. These data are consistent with the observations of Suerbaum et al.(PNAS 1998;95:12619) that selective sweeps are rare in H. pylori populations, & that the 5'and 3'regions of rnr are subject to different selective pressure. Linkage disequilibrium analysis suggests free recombination but the deduced small size of the recombination unit precludes definitive ascertainment of recombination frequency.

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