The rapid emergence of antibiotic resistant bacterial pathogens constitutes a critical problem in healthcare and requires the development of novel treatments. Potential strategies include the exploitation of microbial social interactions based on public goods, which are produced at a fitness cost by cooperative microorganisms, but can be exploited by cheaters that do not produce these goods. Cheater invasion has been proposed as a ‘Trojan horse’ approach to infiltrate pathogen populations with strains deploying built-in weaknesses (e.g., sensitiveness to antibiotics). However, previous attempts have been often unsuccessful because population invasion by cheaters was prevented by various mechanisms including the presence of spatial structure (e.g., growth in biofilms), which limits the diffusion and exploitation of public goods. Here we followed an alternative approach and examined whether the manipulation of public good uptake and not its production could result in potential ‘Trojan horses’ suitable for population invasion. We focused on the siderophore pyoverdine produced by the human pathogen Pseudomonas aeruginosa MPAO1 and manipulated its uptake by deleting and/or overexpressing the pyoverdine primary (FpvA) and secondary (FpvB) receptors. We found that receptor synthesis feeds back on pyoverdine production and uptake rates, which led to strains with altered pyoverdine-associated costs and benefits. Moreover, we found that the receptor FpvB was advantageous under iron-limited conditions but revealed hidden costs in the presence of an antibiotic stressor (gentamicin). As a consequence, FpvB mutants became the fittest strain under gentamicin exposure, displacing the wildtype in liquid cultures, and in biofilms and during infections of the wax moth larvae Galleria mellonella, which both represent structured environments. Our findings reveal that an evolutionary trade-off associated with the costs and benefits of a versatile pyoverdine uptake strategy can be harnessed for devising a Trojan-horse candidate for medical interventions.

抗生素耐药性细菌病原体的迅速出现构成了医疗保健中的一个关键问题，需要开发新的治疗方法。潜在的策略包括利用基于公共物品的微生物社会互动，这些公共物品是由合作微生物以适应性成本生产的，但可以被不生产这些物品的作弊者利用。欺骗者入侵已被提议作为一种“特洛伊木马”方法，以利用具有内在弱点（例如，对抗生素的敏感性）的菌株渗透病原体种群。然而，以前的尝试往往不成功，因为各种机制阻止了作弊者的人口入侵，包括空间结构的存在（例如，生物膜的生长），这限制了公共产品的传播和利用。在这里，我们采用了另一种方法，并检查了操纵公共物品的吸收而不是其生产是否会导致适合人口入侵的潜在“特洛伊木马”。我们专注于人类病原体产生的铁载体pyoverdine铜绿假单胞菌MPAO1 并通过删除和/或过表达 pyoverdine 初级 (FpvA) 和次级 (FpvB) 受体来控制其摄取。我们发现受体合成反馈了 pyoverdine 的产生和摄取率，这导致菌株与 pyoverdine 相关的成本和收益发生了变化。此外，我们发现受体 FpvB 在铁限制条件下是有利的，但在存在抗生素压力源（庆大霉素）的情况下显示出隐藏的成本。因此，FpvB 突变体在庆大霉素暴露下成为最适合的菌株，在液体培养、生物膜和蜡蛾幼虫感染期间取代野生型。，它们都代表结构化环境。我们的研究结果表明，可以利用与多功能 pyoverdine 摄取策略的成本和收益相关的进化权衡来设计用于医疗干预的特洛伊木马候选者。