Macroevolution of gastric Helicobacter species unveils interspecies admixture and time of divergence

Abstract

Since the discovery of the human pathogen Helicobacter pylori, various other Helicobacter species have been identified in the stomach of domesticated and wild mammals. To better understand the evolutionary history of these ecologically similar but genetically distinct species, we analyzed 108 gastric Helicobacter genomes and included 54 enterohepatic Helicobacter genomes for comparison purposes. An admixture analysis supported the presence of an ecological barrier, preventing the genetic exchange between the gastric and enterohepatic Helicobacter species, and unraveled many gene flow events within and across species residing in the stomach. As pets can be colonized by multiple gastric Helicobacter species, the genetic exchange between the canine and feline strains was evident, with H. heilmannii and H. bizzozeronii showing the highest interspecies recombination. An admixture between H. pylori (in particular, the ancestral African strains), H. acinonychis from wild felines and H. cetorum from marine mammals was also identified. Because these latter species do not share the same host, this phenomenon is most likely a remaining signal of shared ancestry. A reconstruction of the time of divergence of the gastric Helicobacter spp. revealed that the domestic animal-related Helicobacter species evolved in parallel with H. pylori and its two closest relatives (H. acinonychis and H. cetorum), rather than together.

Review: Other Helicobacter species

“…28,29 Despite the observation of a histologic mild gastritis, all animals were clinically healthy. 29 However, Takemura et al 30 Furthermore, novel enterohepatic Helicobacter species were identified in both marine and terrestrial zoo mammals. 29 However, Takemura et al 30 Furthermore, novel enterohepatic Helicobacter species were identified in both marine and terrestrial zoo mammals.…”

“…They showed that all animals were predominantly infected with Helicobacter heilmannii, the most prevalent feline Helicobacter species. 28,29 Despite the observation of a histologic mild gastritis, all animals were clinically healthy. 28 This suggests that pet-associated gastric Helicobacters cause little or no harm in their natural host, which is in contrast to other members of the NHPH group.…”

“…29 Admixture analyses have supported the presence of boundaries between gastric and enterohepatic Helicobacter populations due to ecological segregation which prevents genetic recombination. 29 Admixture analyses have supported the presence of boundaries between gastric and enterohepatic Helicobacter populations due to ecological segregation which prevents genetic recombination.…”

“…29 This showed that the coalescent for H. pylori and H. cetorum dated to ca. 29 This showed that the coalescent for H. pylori and H. cetorum dated to ca.…”

“…29 Mannion et al 65 also performed a comparative analysis of gastric and enterohepatic Helicobacter genomes to identify genetic determinants involved in host adaptation, niche colonization, and virulence mechanisms. As no signs of admixture events were found between H. pylori (and its two closest relatives) and the porcine, canine, and feline NHPH, it was concluded that these two groups did not evolve together but rather in parallel following a very distinctive evolutionary path.…”