Abstract
Insights into bacterium-host interactions and genome evolution can emerge from comparisons among related species. Here we studied Helicobacter acinonychis (formerly H. acinonyx), a species closely related to the human gastric pathogen Helicobacter pylori. Two groups of strains were identified by randomly amplified polymorphic DNA fingerprinting and gene sequencing: one group from six cheetahs in a U.S. zoo and two lions in a European circus, and the other group from a tiger and a lion-tiger hybrid in the same circus. PCR and DNA sequencing showed that each strain lacked the cag pathogenicity island and contained a degenerate vacuolating cytotoxin (vacA) gene. Analyses of nine other genes (glmM, recA, hp519, glr, cysS, ppa, flaB, flaA, and atpA) revealed a approximately 2% base substitution difference, on average, between the two H. acinonychis groups and a approximately 8% difference between these genes and their homologs in H. pylori reference strains such as 26695. H. acinonychis derivatives that could chronically infect mice were selected and were found to be capable of persistent mixed infection with certain H. pylori strains. Several variants, due variously to recombination or new mutation, were found after 2 months of mixed infection. H. acinonychis ' modest genetic distance from H. pylori, its ability to infect mice, and its ability to coexist and recombine with certain H. pylori strains in vivo should be useful in studies of Helicobacter infection and virulence mechanisms and studies of genome evolution.