Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
Appl Microbiol Biotechnol. 2020 Feb;104(3):1149-1161. doi: 10.1007/s00253-019-10266-7. Epub 2019 Dec 10.
Discovery of multidrug resistance (MDR) in environmental microorganisms provides unique resources for uncovering antibiotic resistomes, which could be vital to predict future emergence of MDR pathogens. Our previous studies indicated that Lysobacter sp. conferred intrinsic resistance to multiple antibiotics at high levels, especially ampicillin, the first broad-spectrum β-lactam antibiotics against both Gram-positive and Gram-negative bacteria. However, the underlying molecular mechanisms for resistance to ampicillin in Lysobacter enzymogenes strain C3 (LeC3) remain unknown. In this study, screening a Tn5 transposon mutant library of LeC3 recovered 12 mutants with decreased ampicillin resistance, and three mutants (i.e., tatC, lebla, and lpp) were selected for further characterization. Our results revealed that genes encoding β-lactamase (lebla) and twin-arginine translocation (tatC) system for β-lactamase transport played a pivotal role in conferring ampicillin resistance in L. enzymogenes. It was also demonstrated that the lpp gene was not only involved in resistance against β-lactams but also conferred resistance to multiple antibiotics in L. enzymogenes. Permeability assay results indicated that decreased MDR in the lpp mutant was in part due to its higher cellular permeability. Furthermore, our results showed that the difference of LeC3 and L. antibioticus strain LaATCC29479 in ampicillin susceptibility was partly due to their differences in cellular permeability, but not due to β-lactamase activities.
环境微生物中多药耐药（MDR）的发现为揭示抗生素耐药组提供了独特的资源，这对于预测未来 MDR 病原体的出现可能至关重要。我们之前的研究表明，Lysobacter sp. 对多种抗生素具有内在的高水平抗性，特别是氨苄青霉素，这是第一种针对革兰氏阳性和革兰氏阴性细菌的广谱β-内酰胺类抗生素。然而，Lysobacter enzymogenes 菌株 C3（LeC3）对氨苄青霉素抗性的潜在分子机制尚不清楚。在这项研究中，筛选了 LeC3 的 Tn5 转座子突变体文库，恢复了 12 个氨苄青霉素抗性降低的突变体，选择了 3 个突变体（tatC、lebla 和 lpp）进行进一步表征。我们的结果表明，编码β-内酰胺酶（lebla）和双精氨酸易位（tatC）系统的基因用于β-内酰胺酶转运，在赋予 L. enzymogenes 氨苄青霉素抗性方面发挥了关键作用。还证明了 lpp 基因不仅参与了β-内酰胺类抗生素的抗性，而且在 L. enzymogenes 中还赋予了对多种抗生素的抗性。渗透性测定结果表明，lpp 突变体中 MDR 的降低部分归因于其更高的细胞通透性。此外，我们的结果表明，LeC3 和 L. antibioticus 菌株 LaATCC29479 在氨苄青霉素敏感性上的差异部分归因于它们在细胞通透性上的差异，而不是由于β-内酰胺酶活性的差异。
