杀鱼爱德华氏菌新型抗酸系统GadBCD的抗酸作用与致病作用

Acidity resistance and pathogenicity of GadBCD system in Edwardsiella piscicida

摘要:

本研究鉴定了鱼类重要致病菌杀鱼爱德华氏菌（Edwardsiella piscicida）抗强酸系统GadBCD及其功能。通过序列分析和共转录实验表明：GadBCD系统由1个谷氨酸脱羧酶、1个谷氨酰胺酶和3个转运体组成，它们组成1个操纵子。 qRT-PCR发现强酸和高温刺激细菌时gadBCD表达基本不变，但过氧化氢和宿主血清刺激时gadBCD表达显著上调。利用同源重组构建了GadBCD系统缺失突变株ΔgadP，通过比较野生株和ΔgadP的生长曲线以及酸性压力下存活率等实验，发现GadBCD系统不仅是杀鱼爱德华氏菌抗中强酸的重要参与者，也是抗强酸所必需的；通过比较野生株和ΔgadP在生物膜形成、运动性、抗宿主血清杀伤、感染细胞等方面的差异，发现GadBCD参与了细菌的毒力。综上所述， GadBCD系统是杀鱼爱德华氏菌重要的抗强酸系统，并参与了细菌的致病作用。

Abstract:

In this study， we identified the important fish pathogenic bacterium， Edwardsiella piscicida， GadBCD， the strong acid resistance system and its function. Sequence analysis and co-transcription experiments showed that the GadBCD system consists of one glutamic acid decarboxylase， one glutaminase and three transporters， which form a manipulator. qRT-PCR revealed that gadBCD expression was largely unchanged upon strong acid and high temperature stimulation of bacteria， but significantly up-regulated upon hydrogen peroxide and host serum stimulation. A GadBCD system deletion mutant strain ΔgadP was constructed using homologous recombination， and experiments comparing the growth curve and survival rate under acidic stress of wild strain and ΔgadP revealed that the GadBCD system is not only an important player in the resistance of E. piscicida to medium to strong acids， but is also required for resistance to strong acids. GadBCD was found to be involved in bacterial virulence by comparing wild strain and ΔgadP in terms of biofilm formation， motility， resistance to host serum killing， and infection of cells. In conclusion， the GadBCD system is an important strong acid resistant system of E. piscicida and is involved in bacterial pathogenesis.