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发光杆菌假定的 MdtABC 外排泵的时空表达在昆虫感染过程中以依赖蛋白酶的方式发生。

Spatiotemporal expression of the putative MdtABC efflux pump of Phtotorhabdus luminescens occurs in a protease-dependent manner during insect infection.

机构信息

Laboratory of Georesources, Geosciences and Environment, Microbiology team, Faculty of Science 2, Lebanese University, Fanar, Lebanon.

INRA, UMR Diversité, Génomes et Interactions Microorganismes-Insectes, Montpellier, France.

出版信息

PLoS One. 2019 Feb 14;14(2):e0212077. doi: 10.1371/journal.pone.0212077. eCollection 2019.

Abstract

Photorhabdus luminescens is an enterobacterium establishing a mutualistic symbiosis with nematodes, that also kills insects after septicaemia and connective tissue colonization. The role of the bacterial mdtABC genes encoding a putative multidrug efflux system from the resistance/nodulation/cell division family was investigated. We showed that a mdtA mutant and the wild type had similar levels of resistance to antibiotics, antimicrobial peptides, metals, detergents and bile salts. The mdtA mutant was also as pathogenic as the wild-type following intrahaemocoel injection in Locusta migratoria, but had a slightly attenuated phenotype in Spodoptera littoralis. A transcriptional fusion of the mdtA promoter (PmdtA) and the green fluorescent protein (gfp) encoding gene was induced by copper in bacteria cultured in vitro. The PmdtA-gfp fusion was strongly induced within bacterial aggregates in the haematopoietic organ during late stages of infection in L. migratoria, whereas it was only weakly expressed in insect plasma throughout infection. A medium supplemented with haematopoietic organ extracts induced the PmdtA-gfp fusion ex vivo, suggesting that site-specific mdtABC expression resulted from insect signals from the haematopoietic organ. Finally, we showed that protease inhibitors abolished ex vivo activity of the PmdtA-gfp fusion in the presence of haematopoietic organ extracts, suggesting that proteolysis by-products play a key role in upregulating the putative MdtABC efflux pump during insect infection with P. luminescens.

摘要

发光杆菌是一种与线虫建立互利共生关系的肠杆菌,在败血症和结缔组织定植后也能杀死昆虫。本研究调查了编码抗性/结节/细胞分裂家族中假定多药外排系统的细菌 mdtABC 基因的作用。我们表明,mdta 突变体和野生型对抗生素、抗菌肽、金属、清洁剂和胆汁盐的耐药性相似。mdta 突变体在注射到中华飞蝗血腔后与野生型一样具有致病性,但在斜纹夜蛾中表现出稍弱的表型。mdta 启动子 (PmdtA) 和编码绿色荧光蛋白 (gfp) 的基因的转录融合在体外培养的细菌中被铜诱导。在中华飞蝗感染后期,PmdtA-gfp 融合在造血器官中的细菌聚集体中被强烈诱导,而在整个感染过程中在昆虫血浆中仅弱表达。在含有造血器官提取物的培养基中,体外诱导 PmdtA-gfp 融合,表明特定部位的 mdtABC 表达是由来自造血器官的昆虫信号引起的。最后,我们表明,蛋白酶抑制剂在存在造血器官提取物的情况下,可使 PmdtA-gfp 融合的体外活性丧失,这表明在昆虫感染发光杆菌时,蛋白酶解产物在调节假定的 MdtABC 外排泵方面发挥关键作用。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/2d2f/6375597/c354fadc3417/pone.0212077.g001.jpg

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