Bacteria swim by rotating long thin helical filaments, each driven at its base by a reversible rotary motor. When the motors of peritrichous cells turn counterclockwise (CCW), their filaments form bundles that drive the cells forward. We imaged fluorescently labeled cells of Escherichia coli with a high-speed charge-coupleddevice camera (500 frames/s) and measured swimming speeds, rotation rates of cell bodies, and rotation rates of flagellar bundles. Using cells stuck to glass, we studied individual filaments, stopping their rotation by exposing the cells to high-intensity light. From these measurements we calculated approximate values for bundle torque and thrust and body torque and drag, and we estimated the filament stiffness. For both immobilized and swimming cells, the motor torque, as estimated using resistive force theory, was significantly lower than the motor torque reported previously. Also, a bundle of several flagella produced little more torque than a single flagellum produced. Motors driving individual filaments frequently changed directions of rotation. Usually, but not always, this led to a change in the handedness of the filament, which went through a sequence of polymorphic transformations, from normal to semicoiled to curly 1 and then, when the motor again spun CCW, back to normal. Motor reversals were necessary, although not always sufficient, to cause changes in filament chirality. Polymorphic transformations among helices having the same handedness occurred without changes in the sign of the applied torque.The peritrichous bacterium Escherichia coli executes a random walk: an alternating sequence of runs (relatively long intervals during which the cell swims smoothly) and tumbles (relatively short intervals during which the cell changes course) (8). A cell is propelled by several helical flagellar filaments, each attached by a hook (a universal joint) to a reversible rotary motor (7). During runs, the filaments coalesce into a bundle that pushes the cell forward (24). When viewed from behind the cell, the bundle rotates counterclockwise (CCW), and, to balance the torque, the cell body rotates clockwise (CW). Tumbles are initiated by CW motor rotation (21). Based on studies of Salmonella using dark-field microscopy, it was thought that the motors change direction synchronously, causing the bundle to fly apart (24,25). Based on studies using fluorescence microscopy, it became apparent that different filaments can change directions at different times and that a tumble can result from a change in direction of as few as one filament (30). During a tumble, the reversed filament comes out of the bundle and transforms from normal (a left-handed helix with a pitch of 2.3 m and a diameter of 0.4 m) to semicoiled (a right-handed helix with half the normal pitch but normal amplitude) and then to curly 1 (a right-handed helix with half the normal pitch and half the normal amplitude). The change in direction of the cell's track generated by the tumble occurs during the transformation from normal to semi...

When vegetative bacteria that can swim are grown in a rich medium on an agar surface, they become multinucleate, elongate, synthesize large numbers of flagella, produce wetting agents, and move across the surface in coordinated packs: they swarm. We examined the motion of swarming Escherichia coli, comparing the motion of individual cells to their motion during swimming. Swarming cells' speeds are comparable to bulk swimming speeds, but very broadly distributed. Their speeds and orientations are correlated over a short distance (several cell lengths), but this correlation is not isotropic. We observe the swirling that is conspicuous in many swarming systems, probably due to increasingly long-lived correlations among cells that associate into groups. The normal run-tumble behavior seen in swimming chemotaxis is largely suppressed, instead, cells are continually reoriented by random jostling by their neighbors, randomizing their directions in a few tenths of a second. At the edge of the swarm, cells often pause, then swim back toward the center of the swarm or along its edge. Local alignment among cells, a necessary condition of many flocking theories, is accomplished by cell body collisions and/or short-range hydrodynamic interactions.

The recipients of NIH Clinical and Translational Science Awards (CTSA) have worked for over a decade to build informatics infrastructure in support of clinical and translational research. This infrastructure has proved invaluable for supporting responses to the current COVID-19 pandemic through direct patient care, clinical decision support, training researchers and practitioners, as well as public health surveillance and clinical research to levels that could not have been accomplished without the years of ground-laying work by the CTSAs. In this paper, we provide a perspective on our COVID-19 work and present relevant results of a survey of CTSA sites to broaden our understanding of the key features of their informatics programs, the informatics-related challenges they have experienced under COVID-19, and some of the innovations and solutions they developed in response to the pandemic. Responses demonstrated increased reliance by healthcare providers and researchers on access to electronic health record data, both for local needs and for sharing with other institutions and national consortia. The initial work of the CTSAs on data capture, standards, interchange and sharing policies all contributed to solutions, best illustrated by the creation, in record time, of a national clinical data repository in the National COVID Cohort Collaborative (N3C). The survey data support seven recommendations for areas of informatics and public health investment and further study to support clinical and translational research in the post-COVID-19 era.

Human research projects must have a scientifically valid study design, analytic plan, and be operationally feasible in order to be successfully completed and thus to have translational impact. To ensure this, institutions that conduct clinical research should have a scientific review process prior to submission to the Institutional Review Committee (IRB). This paper reports the Clinical and Translational Science Award (CTSA) Consortium Scientific Review Committee (SRC) Consensus Working Group's proposed framework for a SRC process. Recommendations are provided for institutional support and roles of CTSAs, multisite research, criteria for selection of protocols that should be reviewed, roles of committee members, application process, and committee process. Additionally, to support the SCR process effectively, and to ensure efficiency, the Working Group recommends information technology infrastructures and evaluation metrics to determine outcomes are provided.

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