An acpXL Mutant of Rhizobium leguminosarum bv. phaseoli Lacks 27-Hydroxyoctacosanoic Acid in Its Lipid A and Is Developmentally Delayed during Symbiotic Infection of the Determinate Nodulating Host Plant Phaseolus vulgaris
An acpXL Mutant of Rhizobium leguminosarum bv. phaseoli Lacks 27-Hydroxyoctacosanoic Acid in Its Lipid A and Is Developmentally Delayed during Symbiotic Infection of the Determinate Nodulating Host Plant Phaseolus vulgaris
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DOI：
10.1128/jb.00392-11
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发表时间：
2011-09-01
影响因子：
3.2
通讯作者：
Carlson, Russell W.
中科院分区：
文献类型：
--
作者：
Brown, Dusty B.;Huang, Yu-Chu;Carlson, Russell W.
豆根瘤菌是一种革兰氏阴性细菌，通过细胞内侵入与相容的豆科植物形成固氮共生，并在宿主膜衍生的亚细胞区室中建立持续感染。值得注意的是，在豆类根瘤菌的脂质 A 以及医学相关病原体流产布鲁氏菌、羊种布鲁氏菌、汉赛巴尔通体和嗜肺军团菌的脂质 A 中发现了一种不寻常的超长链脂肪酸 (VLCFA)，这些病原体也能够在细胞内宿主来源的细胞膜中持续存在。这些细菌共生体和病原体各自含有合成 VLCFA 并将其转移到脂质 A 所必需的同源基因区域。该区域内有一个编码特殊酰基载体蛋白 AcpXL 的基因，VLCFA 就构建在该基因上。本研究描述了缺乏 VLCFA 的 acpXL 突变体的生化和感染表型。该突变是在 R. leguminosarum bv 中产生的。菜豆菌株 8002，与菜豆（一种确定结节的豆科植物）形成共生。使用气相色谱和质谱的结构分析表明，突变脂质 A 缺乏 VLCFA。与亲本菌株相比，突变体对去污剂脱氧胆酸盐和十二烷基硫酸盐以及抗菌肽多粘菌素 B 更敏感，表明膜稳定性受到损害。此外，突变体对较高的盐浓度更敏感。通过植物恢复了耐盐性。电镜检查表明，该突变体在寄主植物菜豆共生感染过程中发育迟缓，并产生异常的共生体结构。
Rhizobium leguminosarum is a Gram-negative bacterium that forms nitrogen-fixing symbioses with compatible leguminous plants via intracellular invasion and establishes a persistent infection within host membrane-derived subcellular compartments. Notably, an unusual very-long-chain fatty acid (VLCFA) is found in the lipid A of R. leguminosarum as well as in the lipid A of the medically relevant pathogens Brucella abortus, Brucella melitensis, Bartonella henselae, and Legionella pneumophila, which are also able to persist within intracellular host-derived membranes. These bacterial symbionts and pathogens each contain a homologous gene region necessary for the synthesis and transfer of the VLCFA to the lipid A. Within this region lies a gene that encodes the specialized acyl carrier protein AcpXL, on which the VLCFA is built. This study describes the biochemical and infection phenotypes of an acpXL mutant which lacks the VLCFA. The mutation was created in R. leguminosarum bv. phaseoli strain 8002, which forms symbiosis with Phaseolus vulgaris, a determinate nodulating legume. Structural analysis using gas chromatography and mass spectrometry revealed that the mutant lipid A lacked the VLCFA. Compared to the parent strain, the mutant was more sensitive to the detergents deoxycholate and dodecyl sulfate and the antimicrobial peptide polymyxin B, suggesting a compromise to membrane stability. In addition, the mutant was more sensitive to higher salt concentrations. Passage through the plant restored salt tolerance. Electron microscopic examination showed that the mutant was developmentally delayed during symbiotic infection of the host plant Phaseolus vulgaris and produced abnormal symbiosome structures.