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posted 10. October 2005 10:17
Gain and Loss of Multiple Genes During the Evolution of Helicobacter pylori
Source: PLoS Gentics
Volume 1 | Issue 4 | OCTOBER 2005
Helga Gressmann, Bodo Linz, Rohit Ghai, Klaus-Peter Pleissner, Ralph Schlapbach, Yoshio Yamaoka, Christian Kraft, Sebastian Suerbaum, Thomas F. Meyer, Mark Achtman
Sequence diversity and gene content distinguish most isolates of Helicobacter pylori. Even greater sequence differences differentiate distinct populations of H. pylori from different continents, but it was not clear whether these populations also differ in gene content. To address this question, we tested 56 globally representative strains of H. pylori and four strains of Helicobacter acinonychis with whole genome microarrays. Of the weighted average of 1,531 genes present in the two sequenced genomes, 25% are absent in at least one strain of H. pylori and 21% were absent or variable in H. acinonychis. We extrapolate that the core genome present in all isolates of H. pylori contains 1,111 genes. Variable genes tend to be small and possess unusual GC content; many of them have probably been imported by horizontal gene transfer. Phylogenetic trees based on the microarray data differ from those based on sequences of seven genes from the core genome. These discrepancies are due to homoplasies resulting from independent gene loss by deletion or recombination in multiple strains, which distort phylogenetic patterns. The patterns of these discrepancies versus population structure allow a reconstruction of the timing of the acquisition of variable genes within this species. Variable genes that are located within the cag pathogenicity island were apparently first acquired en bloc after speciation. In contrast, most other variable genes are of unknown function or encode restriction/modification enzymes, transposases, or outer membrane proteins. These seem to have been acquired prior to speciation of H. pylori and were subsequently lost by convergent evolution within individual strains. Thus, the use of microarrays can reveal patterns of gene gain or loss when examined within a phylogenetic context that is based on sequences of core genes.
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Read the full research article at PLoS Genetics
Editor: Takashi Gojobori, National Institute of Genetics, Japan
Received: May 18, 2005; Accepted: August 26, 2005; Published: October 7, 2005
DOI: 10.1371/journal.pgen.0010043
Copyright: © 2005 Gressmann et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
* To whom correspondence should be addressed. E-mail: achtman@mpiib-berlin.mpg.de
Citation: Gressmann H, Linz B, Ghai R, Pleissner KP, Schlapbach R, et al. (2005) Gain and Loss of Multiple Genes During the Evolution of Helicobacter pylori. PLoS Genet 1(4): e43
[ 10. October 2005, 10:20: Message edited by: ISCID News Editor ]
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