单核细胞增生李斯特菌抗酸应激机制

Acid tolerance of Listeria monocytogenes

单核细胞增生李斯特菌(Listeria monocytogenes,简称单增李斯特菌)是重要的人畜共患食源性病原,在青贮饲料、发酵食品、宿主胃内以及巨噬细胞吞噬体内都会遭遇酸应激。该菌有多种抗酸应激系统,如F0F1-ATPase、谷氨酸脱羧酶(Glutamate decarboxylase system,GAD)、精氨酸脱亚胺酶(Arginine deiminase,ADI)、鲱氨酸脱亚胺酶(Agmatine deiminase,Ag DI)系统等。在环境pH(pHex)4.5条件下可维持其细胞内pH(pHi)稳态,在pHex 3.5时仍能存活;用温和酸应激(pHex 4.5)预处理单增李斯特菌,可以通过酸耐受反应(Acid tolerance response)提高其在致死性酸性环境中的存活率,这一过程受σB正调控,即σB激活可以保护单增李斯特菌应对多种环境应激。因此,σB可以作为新型抗菌药物的靶标。更为重要的是,弱酸性发酵食品要严格控制李斯特菌的污染,以降低消费者的感染风险。

Listeria monocytogenes, an important zoonotic foodborne pathogen, encounters acidic environments such as silage, fermented food, stomach and phagolysosomes. It contains a number of enzyme systems to deal with acid stress： F0 F1-ATPase, glutamate decarboxylase, arginine deiminase and agmatine deiminase. The bacterium could maintain its intracellular pH（pHi） homeostasis when exposed to environmental pH（pHex） 4.5, survives well in pHex 3.5. Preexposure of L. monocytogenes cells to mild acid stress（pHex 4.5） could induce acid tolerance response（ATR） that could render them more resistant to fatal acidic stress. Sig B（σB） is a positive regulator of ATR, enabling the bacterium to better cope with environmental stresses. Therefore, σB could be a target for development of novel antibacterial drugs. Stringent control of L. monocytogenes contamination in fermented food is of great importance to minimize the risk of listeria infections to consumers.