The ecology of interspecies recombination among the zoonotic bacterium Campylobacter

Horizontal gene transfer (HGT) can allow traits that have
evolved in one bacterial species to transfer to another. This has potential to
rapidly promote new adaptive trajectories such as zoonotic transfer or
antimicrobial resistance. However, for this to occur requires gaps to align in barriers to recombination within a given time frame. Chief among these barriers is the
physical separation of species with distinct ecologies in separate niches.
Within the genus Campylobacter there are species with divergent
ecologies, from rarely isolated single host specialists to multi-host
generalist species that are among the most common global causes of human
bacterial gastroenteritis. Here, by characterising these contrasting ecologies,
we are able to quantify HGT among sympatric and allopatric species in
natural populations. Analysing recipient and donor population ancestry among
genomes from 30 Campylobacter species
we show that cohabitation in the same host can lead to a 6-fold increase in HGT
between species. This accounts for up to 30% of all SNPs within a given species
and identifies highly recombinogenic genes with functions including host
adaptation and antimicrobial resistance. As described in some animal and plant
species, ecological factors are a major evolutionary force for speciation in
bacteria and changes to the host landscape can promote partial convergence of
distinct species through HGT.

水平基因转移（HGT）允许某一细菌物种演化出的性状转移到另一物种。这一过程有可能迅速促进新的适应性进化轨迹，如动物源性传播或抗菌药物耐药性的产生。然而，要实现这一目标，需要在给定的时间框架内，使重组的障碍出现间隙对齐。其中最为重要的障碍是具有不同生态学特征的物种在各自生态位中的物理分离。在弯曲菌属中，存在生态学差异显著的物种，从罕见分离的单宿主专性物种到多宿主泛性物种，后者是全球最常见的导致人类细菌性胃肠炎的原因之一。在本研究中，通过对这些对比鲜明的生态学特征进行表征，我们得以量化自然种群中同域和异域物种间的水平基因转移。通过对来自30种弯曲菌的基因组进行分析，我们发现同一宿主共栖可能导致物种间水平基因转移增加6倍。这解释了特定物种中高达30%的单一核苷酸多态性（SNPs），并识别出具有宿主适应性和抗菌药物耐药性等功能的高度重组基因。正如在一些动物和植物物种中所述，生态因素是细菌物种分化的主要进化动力，而宿主景观的变化可以通过水平基因转移促进不同物种的部分趋同。