Overproduction of the multidrug efflux pump MexEF-OprN does not impair Pseudomonas aeruginosa fitness in competition tests, but produces specific changes in bacterial regulatory networks
Overproduction of the multidrug efflux pump MexEF-OprN does not impair Pseudomonas aeruginosa fitness in competition tests, but produces specific changes in bacterial regulatory networks
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DOI：
10.1111/j.1462-2920.2012.02727.x
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发表时间：
2012-08-01
影响因子：
5.1
通讯作者：
Luis Martinez, Jose
中科院分区：
文献类型：
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作者：
Olivares, Jorge;Alvarez-Ortega, Carolina;Luis Martinez, Jose
人们通常认为，获得抗生素耐药性会导致非特异性的适应成本。我们测试了另一种假设，即获得抗生素耐药性可能并不总是会给微生物带来一般的负担，如竞争测试中所测量的那样，而是导致细菌生理的特定变化。为此，我们研究了多药外排泵MexEF-OprN的过度生产对铜绿假单胞菌的影响，这是由于MexEF-oprN基因的转录激活因子MEXT的结构性激活所致。我们发现，在经典的竞争测试中，MexEF-OprN的过表达并不会导致铜绿假单胞菌适合度的显著下降，这表明没有较大的代谢负担，并且只有在特定条件下才可能观察到任何可能的负面影响。转录分析表明，MexEF-OprN的过表达导致几个群体感应调节基因的表达减少。我们将这种表型追溯到PQS生产的延迟，这是由于PQS前体Kynurenine通过外排泵排出所致。VI型分泌物也受到损害。秀丽隐杆线虫模型表明，MexEF-OprN的过量生产削弱了铜绿假单胞菌的毒力。这种作用主要是由于外排泵的活性，而不是MEXT，尽管后者调节III型和VI型分泌。总之，这些数据表明，抗生素耐药性可以在细菌调控网络中产生修改，从而对特定生态系统中的细菌行为产生相关后果，包括受感染的宿主。
It is generally assumed that acquisition of antibiotic resistance leads to non-specific fitness costs. We have tested the alternative hypothesis that acquisition of antibiotic resistance may not always produce a general burden to the microorganisms, as measured in competition tests, but rather lead to specific changes in bacterial physiology. To this end we studied the effect of overproducing the multidrug efflux pump MexEF-OprN on Pseudomonas aeruginosa due to a constitutive activation of MexT, the transcriptional activator of the mexEF-oprN genes. We found that overexpression of MexEF-OprN does not cause a significant decrease in P. aeruginosa fitness in classical competition tests, indicating the absence of a large metabolic burden and that any possible negative effects might be observed only under specific conditions. Transcriptomic analyses revealed that overexpression of MexEF-OprN results in reduced expression of several quorum-sensing regulated genes. We traced back this phenotype to a delay in PQS production due to extrusion of kynurenine, a PQS precursor, through the efflux pump. Type VI secretion was also impaired. A Caenorhabditis elegans model demonstrated that overproduction of MexEF-OprN impairs virulence in P. aeruginosa. This effect was mainly due to the activity of the efflux pump, and not to MexT, despite the fact that the latter regulates Type III and Type VI secretion. Altogether, these data indicate that antibiotic resistance can produce modifications in the bacterial regulatory networks with relevant consequences for the bacterial behaviour in specific ecosystems, including the infected host.