Indole-Induced Reversion of Intrinsic Multiantibiotic Resistance in Lysobacter enzymogenes
Indole-Induced Reversion of Intrinsic Multiantibiotic Resistance in Lysobacter enzymogenes
复制标题
DOI：
10.1128/aem.00995-17
复制
发表时间：
2017-09-01
影响因子：
4.4
通讯作者：
Du, Liangcheng
中科院分区：
文献类型：
--
作者：
Han, Yong;Wang, Yan;Du, Liangcheng
溶杆菌是一组环境细菌，正在成为一种新的抗生素来源。溶杆菌的一个特征是对多种抗生素的内在耐药性，这一点还没有被研究过。为了了解耐药机制，我们测试了阻断双组分调节系统(TCSs)对抗生素高产产生菌溶杆菌酶基因耐药性的影响。在用广泛存在的TCS QSec/QseB的抑制剂LED209处理后，产酶乳杆菌产生了大量在未经处理的培养物中几乎检测不到的未知代谢物。随后的核磁共振结构分析意外地揭示了该代谢物为吲哚。肾上腺素也显著诱导吲哚的产生，肾上腺素是QSec/QseB的已知调节剂。接下来，我们在L酶基因中发现了两个TCS基因，即L酶基因QSec(Le-qSec)和Le-qseB，并且发现Le-qSec和Le-qseB的突变也导致了吲哚产量的急剧增加。然后，我们化学合成了一种可以标记细胞的荧光吲哚探针。该探针清晰地标记了Le-qseB(细胞质反应调节因子)突变体，而没有标记LeqseC(膜传感器)突变体。此前有报道称，吲哚可增强细菌对抗生素的耐药性。因此，我们测试了在阻断Le-qSec和Le-qseB后，L.酶基因中吲哚产量的急剧增加是否会导致抗生素耐药性的增强。令人惊讶的是，我们发现吲哚导致内在的多重抗生素耐药细菌L.酶基因变得敏感。LeQseC中保守氨基酸的点突变也导致了抗生素敏感性。因为吲哚被认为是种间信号，所以这些发现可能有意义。重要的是，环境细菌溶杆菌是一种新的抗生素化合物来源，并表现出内在的抗生素耐药性。在这里，我们发现，通过抑制剂或基因缺失使双组分调节系统(TCS)失活会显著增加乳杆菌酶基因中代谢物的产生水平，该代谢物被鉴定为吲哚。我们化学合成了一种吲哚荧光探针，发现它可以标记TCS细胞质反应调节因子的野生型和突变体，但不能标记TCS膜传感器的突变体。吲哚治疗导致固有的多重耐药细菌L.酶基因对抗生素敏感。TCS传感器的突变也导致了抗生素敏感性。由于吲哚被认为是肠道微生物区系和哺乳动物宿主之间的物种间信号，因此观察到吲哚可能使固有耐药的L酶基因对常见抗生素敏感可能具有一定的意义。
Lysobacter species are a group of environmental bacteria that are emerging as a new source of antibiotics. One characteristic of Lysobacter is intrinsic resistance to multiple antibiotics, which had not been studied. To understand the resistance mechanism, we tested the effect of blocking two-component regulatory systems (TCSs) on the antibiotic resistance of Lysobacter enzymogenes, a prolific producer of antibiotics. Upon treatment with LED209, an inhibitor of the widespread TCS QseC/QseB, L. enzymogenes produced a large amount of an unknown metabolite that was barely detectable in the untreated culture. Subsequent structural elucidation by nuclear magnetic resonance (NMR) unexpectedly revealed that the metabolite was indole. Indole production was also markedly induced by adrenaline, a known modulator of QseC/QseB. Next, we identified two TCS genes, L. enzymogenes qseC (Le-qseC) and Le-qseB, in L. enzymogenes and found that mutations of Le-qseC and Le-qseB also led to a dramatic increase in indole production. We then chemically synthesized a fluorescent indole probe that could label the cells. While the Le-qseB (cytoplasmic response regulator) mutant was clearly labeled by the probe, the LeqseC (membrane sensor) mutant was not labeled. It was reported previously that indole can enhance antibiotic resistance in bacteria. Therefore, we tested if the dramatic increase in the level of indole production in L. enzymogenes upon blocking of Le-qseC and Le-qseB would lead to enhanced antibiotic resistance. Surprisingly, we found that indole caused the intrinsically multiantibiotic-resistant bacterium L. enzymogenes to become susceptible. Point mutations at conserved amino acids in LeQseC also led to antibiotic susceptibility. Because indole is known as an interspecies signal, these findings may have implications.IMPORTANCE The environmental bacterium Lysobacter is a new source of antibiotic compounds and exhibits intrinsic antibiotic resistance. Here, we found that the inactivation of a two-component regulatory system (TCS) by an inhibitor or by gene deletion led to a remarkable increase in the level of production of a metabolite in L. enzymogenes, and this metabolite was identified to be indole. We chemically synthesized a fluorescent indole probe and found that it could label the wild type and a mutant of the TCS cytoplasmic response regulator but not a mutant of the TCS membrane sensor. Indole treatment caused the intrinsically multidrug-resistant bacterium L. enzymogenes to be susceptible to antibiotics. Mutations of the TCS sensor also led to antibiotic susceptibility. Because indole is known as an interspecies signal between gut microbiota and mammalian hosts, the observation that indole could render intrinsically resistant L. enzymogenes susceptible to common antibiotics may have implications.