Identification and functional characterization of a Xenorhabdus nematophila oligopeptide permease
Identification and functional characterization of a Xenorhabdus nematophila oligopeptide permease
复制标题
DOI：
10.1128/aem.70.9.5621-5627.2004
复制
发表时间：
2004-09-01
影响因子：
4.4
通讯作者：
Goodrich-Blair, H
中科院分区：
文献类型：
--
作者：
Orchard, SS;Goodrich-Blair, H
嗜线虫致病杆菌（Xenorhabdus nematophila）是斯氏线虫（Steinernema carpocapsae）的共生菌，也是昆虫的病原菌。目前，尚不清楚该细菌在这些宿主环境中利用哪些营养物质来生长繁殖。在其他共生细菌中，寡肽通透酶已被证明在与宿主的相互作用中起重要作用，因此我们试图确定寡肽摄取对于嗜线虫致病杆菌在实验室或宿主环境中的生长或共生功能是否必不可少。我们鉴定出了一个嗜线虫致病杆菌的寡肽通透酶（opp）操纵子，它包含两个连续的oppA基因，预计可编码寡肽结合蛋白，以及可能的通透酶编码基因oppB、oppC、oppD和oppF。肽喂养研究表明，这个opp操纵子编码一种有功能的寡肽通透酶。我们构建了oppA、oppA或oppB发生突变的菌株，并检测了每个突变菌株在富含肽的实验室培养基中生长以及与两种宿主相互作用的能力。我们发现opp突变菌株在实验室培养基和从幼虫昆虫中分离出的血淋巴中的生长表型发生了改变。然而，opp突变菌株能够启动并维持共生和致病的宿主相互作用。这些数据表明，opp基因使嗜线虫致病杆菌能够利用肽作为营养源，但这一功能对于嗜线虫致病杆菌在其任一宿主生态位中的生存并非必不可少。据我们所知，这项研究是对寡肽转运在介导无脊椎动物 - 细菌共生相互作用中作用的首次实验分析。
The bacterium Xenorhabdus nematophila is a mutualist of Steinernema carpocapsae nematodes and a pathogen of insects. Presently, it is not known what nutrients the bacterium uses to thrive in these host environments. In other symbiotic bacteria, oligopeptide permeases have been shown to be important in host interactions, and we therefore sought to determine if oligopeptide uptake is essential for growth or symbiotic functions of X. nematophila in laboratory or host environments. We identified an X. nematophila oligopeptide permease (opp) operon of two sequential oppA genes, predicted to encode oligopeptide-binding proteins, and putative permease-encoding genes oppB, oppC, oppD, and oppF. Peptide-feeding studies indicated that this opp operon encodes a functional oligopeptide permease. We constructed strains with mutations in oppA, oppA, or oppB and examined the ability of each mutant strain to grow in a peptide-rich laboratory medium and to interact with the two hosts. We found that the opp mutant strains had altered growth phenotypes in the laboratory medium and in hemolymph isolated from larval insects. However, the opp mutant strains were capable of initiating and maintaining both mutualistic and pathogenic host interactions. These data demonstrate that the opp genes allow X. nematophila to utilize peptides as a nutrient source but that this function is not essential for the existence of X. nematophila in either of its host niches. To our knowledge, this study represents the first experimental analysis of the role of oligopeptide transport in mediating a mutualistic invertebrate-bacterium interaction.