人类生物学在线 Biological Anthropology online's Archiver

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198401 发表于 2013-9-24 09:43

巴卡俾格米人幽门螺杆菌

Recent Acquisition of Helicobacter pylori by Baka Pygmies

Sandra Nell etc.

Abstract[font=arial, sans-serif][size=13px]Both anatomically modern humans and the gastric pathogen [i]Helicobacter pylori[/i] originated in Africa, and both species have been associated for at least 100,000 years. Seven geographically distinct [i]H. pylori[/i] populations exist, three of which are indigenous to Africa: hpAfrica1, hpAfrica2, and hpNEAfrica. The oldest and most divergent population, hpAfrica2, evolved within San hunter-gatherers, who represent one of the deepest branches of the human population tree. Anticipating the presence of ancient [i]H. pylori[/i] lineages within all hunter-gatherer populations, we investigated the prevalence and population structure of [i]H. pylori[/i] within Baka Pygmies in Cameroon. Gastric biopsies were obtained by esophagogastroduodenoscopy from 77 Baka from two geographically separated populations, and from 101 non-Baka individuals from neighboring agriculturalist populations, and subsequently cultured for [i]H. pylori[/i]. Unexpectedly, Baka Pygmies showed a significantly lower [i]H. pylori[/i] infection rate (20.8%) than non-Baka (80.2%). We generated multilocus haplotypes for each [i]H. pylori[/i] isolate by DNA sequencing, but were not able to identify Baka-specific lineages, and most isolates in our sample were assigned to hpNEAfrica or hpAfrica1. The population hpNEAfrica, a marker for the expansion of the Nilo-Saharan language family, was divided into East African and Central West African subpopulations. Similarly, a new hpAfrica1 subpopulation, identified mainly among Cameroonians, supports eastern and western expansions of Bantu languages. An age-structured transmission model shows that the low [i]H. pylori[/i] prevalence among Baka Pygmies is achievable within the timeframe of a few hundred years and suggests that demographic factors such as small population size and unusually low life expectancy can lead to the eradication of[i]H. pylori[/i] from individual human populations. The Baka were thus either [i]H. pylori[/i]-free or lost their ancient lineages during past demographic fluctuations. Using coalescent simulations and phylogenetic inference, we show that Baka almost certainly acquired their extant [i]H. pylori[/i]through secondary contact with their agriculturalist neighbors.[/size][/font]

[font=arial, sans-serif][size=13px][url=http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1003775]http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1003775[/url][/size][/font]

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