细菌基因组编码各种多药外排泵(MDR),其适应性优势的具体条件尚不清楚。我们证明外排泵MdtEF-TolC,在大肠杆菌中,在暴露于极端酸(pH2)期间赋予健身优势。我们的流式细胞术方法揭示了胆汁酸(主要的泵底物)和水杨酸之间的pH依赖性适应性权衡,一种渗透膜的芳香酸,可诱导耐药性调节子,但会消耗质子动力(PMF)。PMF驱动MdtEF-TolC和相关泵,如AcrAB-TolC。在有或没有水杨酸盐或胆汁酸的情况下,mdtE的缺失(伴随泵MdtEF-TolC的丢失)增加了菌株在生长过程中的相对适合度。然而,当生长周期包括在pH2(低于pH生长范围)下孵育2小时时,MdtEF-TolC具有健身优势。健身优势需要胆盐,但由于水杨酸盐的存在而降低,其摄取被酸放大。为了比较,AcrAB-TolC,胆汁酸的主要外排泵,在生长周期中有或没有酸暴露的情况下,赋予了PMF依赖的健康优势。不同的MDR泵,EmrAB-TolC,在胆汁酸存在的情况下,生长过程中没有选择性益处。没有胆汁酸,当暴露于pH2时,所有三种MDR泵都会产生大量的水杨酸盐健身费用。这些结果与低pH下水杨酸盐的吸收增加一致。总的来说,我们发现MdtEF-TolC是一种适用于短暂的极端酸暴露的MDR泵,低pH会增加药物泵依赖水杨酸盐的适应性成本.重要性抗生素和其他到达肠道的药物必须通过胃酸。然而,对极端酸如何调节药物对肠道细菌的作用知之甚少。我们发现,极端的酸暴露会导致多药泵的健身优势,否则会产生健身成本。同时,极端酸放大了水杨酸盐选择对多药泵的影响。因此,有机酸和胃酸在调节肠道微生物群中的多药耐药中起重要作用。我们的流式细胞术测定法提供了一种方法来测量极端酸暴露于各种膜可溶性有机酸的适应性影响。包括植物来源的营养素和药剂。可以设计治疗性酸来控制环境和宿主相关栖息地中多药泵的流行。
Bacterial genomes encode various multidrug efflux pumps (MDR) whose specific conditions for fitness advantage are unknown. We show that the efflux pump MdtEF-TolC, in Escherichia coli, confers a fitness advantage during exposure to extreme acid (pH 2). Our flow cytometry method revealed pH-dependent fitness trade-offs between bile acids (a major pump substrate) and salicylic acid, a membrane-permeant aromatic acid that induces a drug resistance regulon but depletes proton motive force (PMF). The PMF drives MdtEF-TolC and related pumps such as AcrAB-TolC. Deletion of mdtE (with loss of the pump MdtEF-TolC) increased the strain\'s relative fitness during growth with or without salicylate or bile acids. However, when the growth cycle included a 2-h incubation at pH 2 (below the pH growth range), MdtEF-TolC conferred a fitness advantage. The fitness advantage required bile salts but was decreased by the presence of salicylate, whose uptake is amplified by acid. For comparison, AcrAB-TolC, the primary efflux pump for bile acids, conferred a PMF-dependent fitness advantage with or without acid exposure in the growth cycle. A different MDR pump, EmrAB-TolC, conferred no selective benefit during growth in the presence of bile acids. Without bile acids, all three MDR pumps incurred a large fitness cost with salicylate when exposed at pH 2. These results are consistent with the increased uptake of salicylate at low pH. Overall, we showed that MdtEF-TolC is an MDR pump adapted for transient extreme-acid exposure and that low pH amplifies the salicylate-dependent fitness cost for drug pumps. IMPORTANCE Antibiotics and other drugs that reach the gut must pass through stomach acid. However, little is known of how extreme acid modulates the effect of drugs on gut bacteria. We find that extreme-acid exposure leads to a fitness advantage for a multidrug pump that otherwise incurs a fitness cost. At the same time, extreme acid amplifies the effect of salicylate selection against multidrug pumps. Thus, organic acids and stomach acid could play important roles in regulating multidrug resistance in the gut microbiome. Our flow cytometry assay provides a way to measure the fitness effects of extreme-acid exposure to various membrane-soluble organic acids, including plant-derived nutrients and pharmaceutical agents. Therapeutic acids might be devised to control the prevalence of multidrug pumps in environmental and host-associated habitats.