Horizontal gene transfer, the acquisition of genes across species boundaries, is a major source of novel phenotypes that enables microbes to rapidly adapt to new environments. How the transferred gene alters the growth – fitness – of the new host affects the success of the horizontal gene transfer event and how rapidly the gene spreads in the population. Several selective barriers – factors that impact the fitness effect of the transferred gene – have been suggested to impede the likelihood of horizontal transmission, however experimental evidence is scarce. The objective of this study was to determine the fitness effects of orthologous genes transferred from Salmonella enterica serovar Typhimurium to Escherichia coli to identify the selective barriers using highly precise experimental measurements. We found that most gene transfers result in strong fitness costs. Previously identified evolutionary barriers — gene function and the number of protein-protein interactions — did not predict the fitness effects of transferred genes. In contrast, dosage sensitivity, gene length, and the intrinsic protein disorder significantly impact the likelihood of a successful horizontal transfer. While computational approaches have been successful in describing long-term barriers to horizontal gene transfer, our experimental results identified previously underappreciated barriers that determine the fitness effects of newly transferred genes, and hence their short-term eco-evolutionary dynamics.

中文翻译：

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水平基因转移进化障碍的实验测定


水平基因转移，即跨越物种边界的基因获取，是新表型的主要来源，使微生物能够快速适应新环境。转移的基因如何改变新宿主的生长（适应度）会影响水平基因转移事件的成功以及基因在群体中传播的速度。一些选择性障碍——影响转移基因适应性效应的因素——被认为可以阻碍水平传播的可能性，但实验证据很少。本研究的目的是确定从鼠伤寒沙门氏菌转移到大肠杆菌的直系同源基因的适应性效应，以使用高精度的实验测量来识别选择性障碍。我们发现大多数基因转移都会导致巨大的适应成本。之前发现的进化障碍——基因功能和蛋白质-蛋白质相互作用的数量——并不能预测转移基因的适应性效应。相反，剂量敏感性、基因长度和内在蛋白质紊乱显着影响水平转移成功的可能性。虽然计算方法已经成功地描述了水平基因转移的长期障碍，但我们的实验结果发现了以前未被充分认识的障碍，这些障碍决定了新转移基因的适应性效应，从而决定了它们的短期生态进化动态。