Conde-Álvarez Raquel, Palacios-Chaves Leyre, Gil-Ramírez Yolanda, Salvador-Bescós Miriam, Bárcena-Varela Marina, Aragón-Aranda Beatriz, Martínez-Gómez Estrella, Zúñiga-Ripa Amaia, de Miguel María J, Bartholomew Toby Leigh, Hanniffy Sean, Grilló María-Jesús, Vences-Guzmán Miguel Ángel, Bengoechea José A, Arce-Gorvel Vilma, Gorvel Jean-Pierre, Moriyón Ignacio, Iriarte Maite
Universidad de Navarra, Facultad de Medicina, Departamento de Microbiología y Parasitología, Instituto de Salud Tropical (ISTUN) e Instituto de Investigación Sanitaria de Navarra (IdISNA), Pamplona, Spain.
Instituto de Agrobiotecnología, Consejo Superior de Investigaciones Científicas - Universidad Pública de Navarra - Gobierno de Navarra, Pamplona, Spain.
Front Microbiol. 2018 Jan 10;8:2657. doi: 10.3389/fmicb.2017.02657. eCollection 2017.
The brucellae are facultative intracellular bacteria that cause a worldwide extended zoonosis. One of the pathogenicity mechanisms of these bacteria is their ability to avoid rapid recognition by innate immunity because of a reduction of the pathogen-associated molecular pattern (PAMP) of the lipopolysaccharide (LPS), free-lipids, and other envelope molecules. We investigated the homologs of , and , three genes that in some pathogens encode enzymes that mask the LPS PAMP by upsetting the core-lipid A charge/hydrophobic balance. , which encodes a putative ethanolamine transferase, carries a frame-shift in but not in other spp. and phylogenetic neighbors like the opportunistic pathogen Consistent with the genomic evidence, a mutant lacked lipid A-linked ethanolamine and displayed increased sensitivity to polymyxin B (a surrogate of innate immunity bactericidal peptides), while carrying displayed increased resistance. encodes a putative phosphatase acting on lipid A or on a free-lipid that is highly conserved in all brucellae and Although we found no evidence of lipid A dephosphorylation, a mutant showed increased polymyxin B sensitivity, suggesting the existence of a hitherto unidentified free-lipid involved in bactericidal peptide resistance. Gene putatively encoding an acyl hydroxylase carries a frame-shift in all brucellae except and is intact in . Free-lipid analysis revealed that corresponded to , the gene coding for the ornithine lipid (OL) acyl hydroxylase active in and , while carrying the of and synthesized hydroxylated OLs. Interestingly, mutants in , or were not attenuated in dendritic cells or mice. This lack of an obvious effect on virulence together with the presence of the intact homolog genes in and but not in other brucellae suggests that LptA, LpxE, or OL β-hydroxylase do not significantly alter the PAMP properties of LPS and free-lipids and are therefore not positively selected during the adaptation to intracellular life.
布鲁氏菌是兼性胞内菌，可引发全球范围内广泛传播的人畜共患病。这些细菌的致病机制之一是，由于脂多糖（LPS）、游离脂质及其他包膜分子的病原体相关分子模式（PAMP）减少，它们能够避免被固有免疫快速识别。我们研究了、和的同源基因，在一些病原体中，这三个基因编码的酶可通过破坏核心脂质A的电荷/疏水平衡来掩盖LPS的PAMP。编码假定乙醇胺转移酶的在中存在移码突变，但在其他种及机会致病菌等系统发育近缘菌中不存在。与基因组证据一致，突变体缺乏与脂质A连接的乙醇胺，对多粘菌素B（一种固有免疫杀菌肽的替代物）的敏感性增加，而携带的则表现出抗性增强。编码假定作用于脂质A或游离脂质的磷酸酶，在所有布鲁氏菌和中高度保守。尽管我们没有发现脂质A去磷酸化的证据，但突变体对多粘菌素B的敏感性增加，这表明存在一种迄今未鉴定的与杀菌肽抗性有关的游离脂质。假定编码酰基羟化酶的基因在除之外的所有布鲁氏菌中都有移码突变，而在中是完整的。游离脂质分析表明，对应于，该基因编码在和中具有活性的鸟氨酸脂质（OL）酰基羟化酶，而携带和的则合成了羟基化的OL。有趣的是，、或的突变体在树突状细胞或小鼠中并未减毒。这种对毒力缺乏明显影响，以及在和中存在完整的同源基因而在其他布鲁氏菌中不存在的情况表明，LptA、LpxE或OLβ-羟化酶不会显著改变LPS和游离脂质的PAMP特性，因此在适应细胞内生活的过程中未被正向选择。
