Real-Time Measurement of Vibrio alginolyticus Polar Flagellar Growth

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題名:	Real-Time Measurement of Vibrio alginolyticus Polar Flagellar Growth
作者:	陳美廷;Chen, Mei-Ting
貢獻者:	物理學系
關鍵詞:	鞭毛;溶藻弧菌;flagella;sheath;vibrio alginolyticus;flagellin
日期:	2017-01-23
上傳時間:	2017-05-05 17:19:15 (UTC+8)
出版者:	國立中央大學
摘要:	細菌鞭毛是根生長於細菌體外的細長管子，此管子會形成螺旋推進器用以驅動細菌運動。鞭毛的形成是一個自我組成的過程，鞭毛蛋白從管子的基部通過管子中心被送到遠端，當它一到達頂端便會立即成為鞭毛的一部份，進而使整根鞭毛長度增加。為了研究這個奈米尺度的自我組成系統，我們開發了一種快速標記鞭毛的方法，我們應用具有高空間和時間解析度的活體螢光影像直接觀測溶藻弧菌鞭毛的生長。與先前的研究相比，我們的結論顯示溶藻弧菌的鞭毛成長速度與長度有高度相關性：鞭毛長度短於1500 奈米，鞭毛以每分鐘50 奈米的速度等速成長，隨著鞭毛長度增長，其成長速度會變慢，首先急劇下降接著趨於平緩，最後，當鞭毛長度為7500 奈米，鞭毛的成長速度為每分鐘9 奈米。我們建立了一個名為injection-diffusion 的模型來解釋我們的結果，由於鞭毛蛋白在管子內短距離的擴散速度很快，所以短鞭毛的鞭毛生長速度主要是由基部鞭毛蛋白輸送進管內的速率所決定；當鞭毛長度增長，鞭毛蛋白的擴散變為有速度限制的，部分的單體會塞在管內，阻礙新的鞭毛蛋白進入管內，鞭毛的生長速度因而劇烈地減慢。我們的結果提供了細菌鞭毛的動態生長過程一個新的觀點。;Bacterial flagella are thin external tubular filaments that form helical propellers to drive swimming in bacteria. Forming flagella is a self-assembly process when partially unfolded flagellum monomers, flagellins, are pumped out and transported through the central channel from its base to the distal end. The secretion apparatus contains six membrane proteins (FlhA, FlhB, FliO, FliP, FliQ and FliR) and three soluble proteins (FliH, FliI, and FliJ) shareing the same structure with type III secretion system which is used solely for secretion. As flagellin reaches the growing end of flagellar filament, it crystallizes immediately and becomes the new extending part of the filament. In order to study this nanometer-size self-assembled system, we have developed a fast flagellar filament labeling assay. We applied in vivo fluorescent imaging to monitor directly the growth of Vibrio alginolyticus polar flagella with high spatial and temporal resolution. In contrast to previous reports, we revealed that the flagellar growth rate of Vibrio alginolyticus is highly length-dependent. When flagellar length is shorter than 1500 nm, the flagellum growth is at a constant rate (50 nm/min). As the flagellum grows longer, the growth rate decays. It drops sharply at first and tends to ease in the long flagella region. It decreases to 9 nm/min when flagellar length is 7500 nm. We built an injection-diffusion model to explain our results. When the flagellum is short, its growth rate is determined primarily by the loading speed at the filament base, since diffusion of flagellin across the short distance in the channel is fast. When the flagellum grows longer, diffusion of flagellin becomes rate-limiting. It causes some flagellar monomers jammed in the channel. III Such blockage slows down the loading of new flagellins into the channel. Therefore,the flagellar growth rate drops dramatically. Our results shed new light on the dynamic building process of this complex extracellular structure.
顯示於類別:	[物理研究所] 博碩士論文

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