肌醇、唾液酸及岩藻糖代谢途径对嗜水气单胞菌致病性的影响

Effects of myo-inositol, sialic acid and L-fucose metabolic pathways on pathogenicity of Aeromonas hydrophila strain NJ-35

摘要:

[目的]调查肌醇、唾液酸以及岩藻糖代谢途径在嗜水气单胞菌感染宿主过程中对细菌致病性的影响。[方法]采用同源重组技术分别缺失嗜水气单胞菌NJ-35株的肌醇代谢相关基因iolC、唾液酸代谢相关基因nanA和岩藻糖代谢相关基因fucK，测定各缺失株对斑马鱼的半数致死量（LD₅₀）；将野生株与缺失株共感染鲫鱼，统计野生株和缺失株在不同组织中的细菌载量。[结果]各代谢相关基因的缺失均成功阻断了菌株对相应底物的降解能力。iolC的缺失导致菌株对斑马鱼的LD₅₀升高近12倍，而nanA和fucK的缺失对LD₅₀没有明显影响。野生株与iolC缺失株共感染鲫鱼，肝脏、脾脏和肾脏中野生株的载量显著高于缺失株，表现出明显的生长优势；nanA和fucK缺失株与野生株共感染鲫鱼，野生株和缺失株载量在各组织中均无明显差异。[结论]肌醇代谢途径在嗜水气单胞菌感染致病过程中发挥重要作用，而唾液酸和岩藻糖代谢途径对细菌无明显影响。

关键词:嗜水气单胞菌;肌醇;唾液酸;岩藻糖;代谢;基因缺失;致病性

Abstract:

[Objective] This study aims to investigate the effect of inositol, sialic acid, and L-fucose metabolic pathways on pathogenicity in the process of Aeromonas hydrophila infection. [Methods] By homologous recombination technology, the genes associated with myo-inositol, sialic acid and L-fucose metabolism, iolC, fucK and nanA, were inactivated. Then fifty percent lethal doses (LD₅₀) of the deletion mutants were determined in zebrafish and the bacterial loads in different tissues were assayed in crucian carp co-infected with the wild-type and its derivative mutant strains. [Results] The inactivation of all the three metabolic genes successfully blocked the ability of A. hydrophila to degrade the corresponding substrates. Deletion of iolC resulted in a nearly 12-fold increase in LD₅₀ in zebrafish, whereas deletion of nanA and fucK had no significant effect on LD₅₀. The bacterial loads of the wild strain were significantly higher than that of the iolC deletion strain in liver, spleen and kidney after co-infection, indicating an obvious competitive growth advantage of the wild strain. But for nanA and fucK mutant strains, after co-infection with the wild strain, there was no significant difference in bacterial loads of the wild-type and its derivative mutant strains in different tissues. [Conclusion] The inositol metabolic pathway plays an important role during A. hydrophila infection, while sialic acid and L-fucose metabolic pathways have no significant effect on the pathogenicity of this bacterium.

Key words:Aeromonas hydrophila;myo-inositol;sialic acid;L-fucose;metabolism;gene deletion;pathogenicity