- 學位論文
靈菌表面移行行為之調控及其與宿主間之交互關係: -SspA, 新的脂蛋白調控靈菌表面移行系統 -2,3-butanediol緩解大鼠模式中脂多醣誘發之急性發炎反應
Swarming regulation and bacteria-host interaction in Serratia marcescens: -A novel lipoprotein SspA regulates S. marcescens swarming -2,3-butanediol, a bacterial metabolite, ameliorates acute inflammatory response induced by LPS in rat model
摘要
Swarming為一種細菌群體在固體表面移行之特殊型態，已知靈菌 (Serratia marcescens) 野生株CH-1在30 ºC時能在固體表面上進行swarming，但在37 ºC時則被抑制。為了解其中的機制，我們利用Tn5跳躍子篩選出能在37 ºC環境下進行swarming的突變株。其中之一突變株破壞在sspA基因的位置，經由序列比對後發現SspA為一全新的脂蛋白，而SspA的破壞可能與此一突變株在37 ºC swarming的行為有關。雖然尚未有直接而全盤的證據指出SspA在調控swarming的過程中所扮演的角色，但根據此一突變株的各種表現型，包括biosurfactant 產生的增加、鞭毛表現量的增加以及細胞附著能力的下降，可能都與SspA的破壞有關，進而導致sspA突變株在37 ºC下的swarming行為。除此之外，由於在突變株溶血素活性的上升，指出了swarming跟S. marcescens致病性的可能關聯。因此，我們另外對於S. marcescens 的致病機轉及其之所以為重要的伺機性病原菌的原因做進一步的探討。在我第二部份的研究發現，在大鼠模式中， S. marcescens的pyruvate代謝產物2,3-butanediol不但明顯抑制由細菌內毒素(脂多醣體)所誘發的急性肺損傷與相關的發炎反應，其效果幾乎與已知為一抗發炎多酚化合物葡萄籽萃取物resveratrol相當，進一步研究則發現2,3-butanediol能夠透過調節NF-κB的訊息傳遞路徑來抑制由脂多醣體所引起的急性發炎反應。因此，2,3-butanediol在細菌感染的過程中，對於宿主的innate免疫反應扮演著負向調控的角色，此結果也暗示了細菌利用其代謝產物逃避宿主免疫系統的可能性。
並列摘要
Swarming in Serratia marcescens is a specialized form of bacterial surface migration. S. marcescens swarms at 30 ºC but not at 37 ºC on 0.8 % LB agar plate. To unravel the underlying mechanisms of the temperature-dependent swarming behavior, transposon mutagenesis was performed to screen for mutants that swarmed at 37 ºC. SspA, a novel lipoprotein, was identified to involve the negative regulation of S. marcescens swarming at 37 ºC. Increased production of biosurfactant, over-synthesis of flagellum and the reduced biofilm formation in sspA mutant S. marcescens SC101 all might contribute to the precocious-swarming behavior of S. marcescens SC101 at 37 ºC. Furthermore, the increased hemolytic activity of precocious-swarming mutant suggested that the regulation of swarming is closely related to the pathogenesis of S. marcescens. Besides, we also asked why S. marcescens is an important nosocomial pathogen. Herein, we showed that gastric intubation of 2,3-butanediol, a pyruvate metabolite produced by S. marcescens, in rats significantly ameliorates acute lung injury and the inflammatory responses induced by S. marcescens derived endotoxin lipopolysaccharide (LPS), with an efficacy comparable to that of the polyphenol compound resveratrol. Such effect was further demonstrated to occur via modulation of the NF-κB signaling pathway. Our results indicated that bacterial metabolite, 2,3-butanediol has a negative regulatory effect on host innate immunity response, suggesting bacteria may use some metabolites for host immune evasion.
參考文獻
延伸閱讀
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