Supporting Online Material Materials and Methods Som Text Figs. S1 to S7 Tables S1 to S3 References Movies S1 to S6 Tuned Responses of Astrocytes and Their Influence on Hemodynamic Signals in the Visual Cortex-猫眼课题宝

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D B Kearns;F. Chu;S. Branda;R. Kolter;R. Losick;F Chu;D. Kearns;P M Coutinho;E. Deleury;G. Davies;B. Henrissat;C Garinot-Schneider;A. Lellouch;R. Geremia;H. Blair;Berg;S. A. Lloyd;H. Tang;X. Wang;S. Billings;D. Blair;N. Thomas;C. Francis;D. J. Xu;Derosier;Irikura;M. Kihara;S. Yamaguchi;H. Sockett;R. Macnab;D L Marykwas;S. A. Schmidt;H. Berg;S M Block;Darnton;L. Turner;S. Rojevsky;G. Darnton;B. Glekas;A. Haldenwang;Y. Camp;S. Le Breton;S. Michaels;G. Mukhopadhyay;D. Ordal;Rudner;Ben-Shahar Yehuda;D. Blair;C. Fuqua;D. Higgins;P. Levin;S. Mukhopadhyay;J. Schummers;Hongbo Yu;M. Sur

EpsE或缺乏motA和motB与计算的B在90 s内的均方根角偏差约80°一致。枯草细胞系由无动力的鞭毛自由旋转布朗运动（支持在线材料）。相比之下，角偏差小得多，约3°，对于E。大肠杆菌细胞被固定的鞭毛栓住（22）。因此，EpsE起着离合器的作用;当EpsE被诱导时，鞭毛表现得好像它们没有动力而不是固定不动。离合器的生物学功能似乎与B有关。这是因为epsE在15个基因的eps操纵子内编码，该操纵子促进生物膜EPS的生物合成并且被生物膜形成的主调节因子SinR抑制。因此，控制单个基因座确保细胞在生物膜形成的同时被固定（图S5 A）。在野生型细胞中，在生物膜聚集体内观察到EpsE的捕获鞭毛和斑点，并且聚集体内的细胞是无柄的（图S6和电影S5）。表达FliG V338 A离合器不敏感等位基因的细胞形成聚集体，但细胞在基质的范围内扭动（电影S6）。我们假设离合器有助于稳定环境中的生物膜，并作为一种故障安全机制，以确保鞭毛不旋转，而细胞被EPS结合。细菌鞭毛由产生1400 pN-nm扭矩的电机驱动，可以以大于100 Hz的频率旋转（23）。当与鞭毛基体相关联时，EpsE使这种强大的生物马达失效，并且以类似于离合器的方式使传动系与动力源分离（图S5 B）。鞭毛功能的离合器控制具有明显的优势，鞭毛基因表达的转录控制调节运动。一些细菌，如E. coli和B. subtilis，每个细胞有许多鞭毛。鞭毛是一个精心制作的，耐用的，能量昂贵的分子机器，简单地关闭从头鞭毛合成并不一定会阻止运动。一旦鞭毛基因表达失活，可能需要多轮细胞分裂来分离预先存在的鞭毛以使其在子细胞中灭绝。相反，离合器只需要合成一种蛋白质来抑制运动。此外，如果生物膜形成过早中止，鞭毛一旦被离合器禁用可能会重新激活，允许细胞绕过鞭毛合成的新投资。而鞭毛的表达和...

EpsE or lacking motA and motB was consistent with a calculated root mean square angular deviation of ~80° in 90 s for a B. subtilis cell tethered by an unpowered flagellum freely rotating by Brownian motion (supporting online material). In contrast, the angular deviation is much less, ~3°, for an E. coli cell tethered by an immobilized flagellum (22). Thus, EpsE acted as a clutch; when EpsE was induced, the flagella behaved as though they were unpowered rather than immobilized. The biological function of the clutch appears to be related to the B. subtilis biofilm because epsE is encoded within the 15-gene eps operon that promotes the biosynthesis of the biofilm EPS and is repressed by SinR, the master regulator of biofilm formation. Therefore, control of a single locus ensures that cells become immobilized con-comitant with biofilm formation (fig. S5A). In wild-type cells, trapped flagella and puncta of EpsE were observed within biofilm aggregates, and the cells within the aggregates were sessile (fig. S6 and movie S5). Cells expressing the FliG V338A clutch-insusceptible allele formed aggregates, but the cells writhed within the confines of the matrix (movie S6). We hypothesize that the clutch helps to stabilize biofilms in the environment and acts as a fail-safe mechanism to ensure that flagella do not rotate while the cells are bound by EPS. The bacterial flagellum, powered by a motor that generates 1400 pN-nm of torque, can rotate at a frequency of greater than 100 Hz (23). EpsE disabled this powerful biological motor when associated with a flagellar basal body and, in a manner similar to that of a clutch, disengaged the drive train from the power source (fig. S5B). Clutch control of flagellar function has distinct advantages over transcriptional control of flagel-lar gene expression for regulating motility. Some bacteria, such as E. coli and B. subtilis, have many flagella per cell. The flagellum is an elaborate , durable, energetically expensive, molecular machine and simply turning off de novo flagellum synthesis does not necessarily arrest motility. Once flagellar gene expression is in-activated, multiple rounds of cell division may be required to segregate preexisting flagella to extinction in daughter cells. In contrast, the clutch requires the synthesis of only a single protein to inhibit motility. Furthermore, if biofilm formation is prematurely aborted, flagella once disabled by the clutch might be reactivated, allowing cells to bypass fresh investment in flagellar synthesis. Whereas flagellum expression and …

Supporting Online Material Materials and Methods Som Text Figs. S1 to S7 Tables S1 to S3 References Movies S1 to S6 Tuned Responses of Astrocytes and Their Influence on Hemodynamic Signals in the Visual Cortex

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