BEGIN:VCALENDAR VERSION:2.0 X-WR-TIMEZONE:Europe/Paris CALSCALE:GREGORIAN METHOD:PUBLISH PRODID:-//SPIP/Plugin Agenda//NONSGML v1.0//FR BEGIN:VEVENT SUMMARY:Bacterial Surface Migration : Force Measurement and Modelling UID:evenement5493 @ DTSTAMP:20181218T140000 DTSTART:20181218T140000 DTEND:20181218T150000 LOCATION:Conference room - LIPhy - Bât E - 140 Avenue de la Physique - St Martin d’Hères. Accès par interphone\, appeler le secrétariat DESCRIPTION:Generation and control of mechanical forces are essential for a wide range of bacterial behaviors including surface migration and colony formation and also play a role for infection by Gram-negative pathogens. Many bacteria employ retractable type-IV pili to generate these nanoscopic forces. Since it is difficult to measure such small forces in a perturbationless fashion\, little is known about how bacteria regulate or adapt their force generation by pili. Here\, I present experimental and theoretical studies of bacterial surface migration. First\, I summarize a study of bacterial cell-substrate traction with Myxococcus xanthus as a model organism. Measurements show that during migration\, individual type-IV pili exert forces around 50 pN deforming the substrate beneath the bacteria. However\, when M. xanthus aggregates into groups\, forces appear upregulated and pili exert more than twice the forces measured with individual cells. Nevertheless\, pilus dynamics remain uncoordinated in groups leading to random tugging with autocorrelation times on the order of one minute. After discussing experimental findings\, I present a model describing the effects of surface properties on bacterial migration. The model predicts a non-linear dependence of migration speed and mean square displacement on substrate properties\, which is in accordance with experimental data. The essence of these effects is explained by an analytical theory. Contact : URL: test.ics STATUS:CONFIRMED END:VEVENT END:VCALENDAR