Smith Derek D N, Nickzad Arvin, Déziel Eric, Stavrinides John
Department of Biology, University of Regina, Regina, Saskatchewan, Canada.
INRS-Institut Armand-Frappier, Laval, Québec, Canada.
mSphere. 2016 Jan 20;1(1). doi: 10.1128/mSphere.00075-15. eCollection 2016 Jan-Feb.
Pantoea is a versatile genus of bacteria with both plant- and animal-pathogenic strains, some of which have been suggested to cause human infections. There is, however, limited knowledge on the potential determinants used for host association and pathogenesis in animal systems. In this study, we used the model host Dictyostelium discoideum to show that isolates of Pantoea ananatis exhibit differential grazing susceptibility, with some being resistant to grazing by the amoebae. We carried out a high-throughput genetic screen of one grazing-resistant isolate, P. ananatis BRT175, using the D. discoideum pathosystem to identify genes responsible for the resistance phenotype. Among the 26 candidate genes involved in grazing resistance, we identified rhlA and rhlB, which we show are involved in the biosynthesis of a biosurfactant that enables swarming motility in P. ananatis BRT175. Using liquid chromatography-mass spectrometry (LC-MS), the biosurfactant was shown to be a glycolipid with monohexose-C10-C10 as the primary congener. We show that this novel glycolipid biosurfactant is cytotoxic to the amoebae and is capable of compromising cellular integrity, leading to cell lysis. The production of this biosurfactant may be important for bacterial survival in the environment and could contribute to the establishment of opportunistic infections. IMPORTANCE The genetic factors used for host interaction by the opportunistic human pathogen Pantoea ananatis are largely unknown. We identified two genes that are important for the production of a biosurfactant that confers grazing resistance against the social amoeba Dictyostelium discoideum. We show that the biosurfactant, which exhibits cytotoxicity toward the amoebae, is a glycolipid that incorporates a hexose rather than rhamnose. The production of this biosurfactant may confer a competitive advantage in the environment and could potentially contribute to the establishment of opportunistic infections.
泛菌属是一类具有多种功能的细菌，包含植物致病菌株和动物致病菌株，其中一些菌株被认为可引发人类感染。然而，关于动物系统中宿主关联和发病机制的潜在决定因素，我们所知有限。在本研究中，我们使用模式宿主盘基网柄菌来表明菠萝泛菌的分离株表现出不同的被吞噬易感性，其中一些对变形虫的吞噬具有抗性。我们利用盘基网柄菌致病系统对一株抗吞噬的分离株——菠萝泛菌BRT175进行了高通量基因筛选，以鉴定负责抗性表型的基因。在参与抗吞噬的26个候选基因中，我们鉴定出了rhlA和rhlB，我们发现它们参与了一种生物表面活性剂的生物合成，这种生物表面活性剂使菠萝泛菌BRT175能够进行群体游动。使用液相色谱 - 质谱联用（LC - MS）分析表明，该生物表面活性剂是一种糖脂，其主要同系物为单己糖 - C10 - C10。我们表明这种新型糖脂生物表面活性剂对变形虫具有细胞毒性，并且能够破坏细胞完整性，导致细胞裂解。这种生物表面活性剂的产生可能对细菌在环境中的生存很重要，并且可能有助于机会性感染的建立。重要性：机会性人类病原体菠萝泛菌用于宿主相互作用的遗传因素在很大程度上尚不清楚。我们鉴定出两个基因，它们对于一种生物表面活性剂的产生很重要，这种生物表面活性剂赋予了对社会性变形虫盘基网柄菌的吞噬抗性。我们表明，这种对变形虫具有细胞毒性的生物表面活性剂是一种包含己糖而非鼠李糖的糖脂。这种生物表面活性剂的产生可能在环境中赋予竞争优势，并可能潜在地有助于机会性感染的建立。
