【24th.May】Mechanical Principles of Biofilm Formation
日期：2017-05-24
閱讀：1186
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TOPIC：Mechanical Principles of Biofilm Formation（細菌菌膜形成的力學機制）
SPEAKER：Dr. Jing Yan, Princeton University（嚴兢博士，普林斯頓大學）
TIME: May 24 (Wednesday) 10:00 am
LOCATION：Room 410, Chemistry Building B （化學B樓410室）
INVITER：Prof. Xinyuan Zhu, Prof. Yongfeng Zhou（朱新遠教授，周永豐教授）????????
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ABSTRACT
Biofilms are surface-associated bacterial communities embedded in an extracellular matrix. Biofilm cells are a major problem in the context of chronic infections, because biofilm dwelling cells have increased antibiotic resistance compared to their planktonic counterparts. Investigations so far have mainly focused on the genetic and regulatory features driving biofilm formation. However, still lacking is a fundamental biophysical and biomechanical understanding of how bacteria, in time and space, build these dense three-dimensional structures.
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During this talk, I will discuss about our recently progress in using Vibrio cholerae as a model biofilm former to reveal the mechanical principles behind biofilm formation. I will first present a new methodology to image living, growing bacterial biofilms at single-cell resolution, and demonstrate how cell-cell adhesion and cell-surface adhesion balance each other to cause V. cholerae biofilms to transition from a two-dimensional branched morphology to an ordered three-dimensional cluster. Next, I will demonstrate how matrix production enables biofilm cells to establish an osmotic pressure differential between the biofilm and the external environment, and use this osmotic pressure to facilitate the biofilm expansion. Finally, I will present various mechanical instabilities that takes place when biofilms grow on soft tissue-like substrates. We also complemented these mechanical studies by genetic analyses and ecological competition experiments to decipher the biological consequences of the biomechanical phenomena observed in bacterial biofilms.
?? 細菌菌膜是細菌依附于各種表面，由細胞外基質包裹而成的團簇。菌膜引起的慢性病很難根治，因為菌膜中的細菌相比于浮游的細菌更具有抗藥性。至今為止的大多數(shù)研究側重于導致菌膜形成的基因及其調控機制，然而我們仍缺少從生物物理和生物力學角度對于菌膜形成機理的理解。
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?? 在這個報告中，我會討論我們近期以弧形霍亂菌為模型生物，從生物力學角度對菌膜形成的研究進展。首先，我們發(fā)展了一種成像技術使得我們能夠在單細胞水平上實時原位觀察菌膜形成的過程。我們發(fā)現(xiàn)細菌之間的結合力和細菌與表面的結合力之間的平衡使得菌膜能夠完成從枝狀的二維結構向緊密有序堆積的三維結構的轉變。其次，我們發(fā)現(xiàn)菌膜中的細菌通過分泌細胞外基質而建立滲透壓梯度，從而獲取養(yǎng)分并幫助其在表面上擴展。最后，我會討論當菌膜在不同的柔性表面上形成時所發(fā)生的力學失穩(wěn)現(xiàn)象。通過對不同菌種的表征和競爭實驗，我們進一步分析了以上力學機理對于菌膜在自然生態(tài)環(huán)境中的影響。
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Short Bio:
Dr. Jing Yan obtained his bachelor degree in the College of Chemistry and Molecular Engineering in Peking University. As a graduate student, he studied soft matter physics in the Department of Materials Science and Engineering at University of Illinois at Urbana-Champaign. During his Ph.D., he developed a series of nonequilibrium colloidal materials driven by external electromagnetic fields. He then transitioned to biology, working at Princeton jointly in the Department of Molecular Biology and Mechanical Engineering, on understanding the formation of bacterial biofilms. He has published a series of research papers in journals including Nature and Nature Materials, and he is now a Burroughs Wellcome Fellow working at the interface between biology and engineering.
?? 嚴兢博士本科畢業(yè)于北京大學化學與分子工程學院。博士期間，他就讀于伊利諾伊大學香檳分校的材料科學與工程系，專攻軟物質物理。在博士期間，他發(fā)展了一系列由外場驅動的非平衡態(tài)膠體材料。博士畢業(yè)后，他轉向生物方向并就職于普利斯頓大學的分子生物系與機械工程系，主要研究方向為細菌菌膜的形成與治理。在博士及博士后期間，其曾在自然，自然材料等雜志上發(fā)表文章，并獲得2016年度美國Burroughs Wellcome基金會的交叉學科成就獎。
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