title: Fast, high-throughput measurement of collective behaviour in a bacterial population.
abstract: Swimming bacteria explore their environment by performing a random walk, which is biased in response to, for example, chemical stimuli, resulting in a collective drift of bacterial populations towards 'a better life'. This phenomenon, called chemotaxis, is one of the best known forms of collective behaviour in bacteria, crucial for bacterial survival and virulence. Both single-cell and macroscopic assays have investigated bacterial behaviours. However, theories that relate the two scales have previously been difficult to test directly. We present an image analysis method, inspired by light scattering, which measures the average collective motion of thousands of bacteria simultaneously. Using this method, a time-varying collective drift as small as 50 nm s(-1) can be measured. The method, validated using simulations, was applied to chemotactic Escherichia coli bacteria in linear gradients of the attractant α-methylaspartate. This enabled us to test a coarse-grained minimal model of chemotaxis. Our results clearly map the onset of receptor methylation, and the transition from linear to logarithmic sensing in the bacterial response to an external chemoeffector. Our method is broadly applicable to problems involving the measurement of collective drift with high time resolution, such as cell migration and fluid flows measurements, and enables fast screening of tactic behaviours.
authors.affiliation: The Rowland Institute at Harvard, 100 Edwin H. Land Boulevard, Cambridge, MA 02142, USA remy.colin@synmikro.mpi-marburg.mpg.de.
authors.forename: R
authors.identifier: http://orcid.org/0000-0001-9051-8003
authors.initials: R
authors.lastname: Colin
authors.affiliation: Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: R
authors.initials: R
authors.lastname: Zhang
authors.affiliation: The Rowland Institute at Harvard, 100 Edwin H. Land Boulevard, Cambridge, MA 02142, USA laurence.wilson@york.ac.uk.
authors.forename: L G
authors.identifier: http://orcid.org/0000-0001-6659-6001
authors.initials: LG
authors.lastname: Wilson
mesh_terms: D000465:Algorithms; D018407:Bacterial Physiological Phenomena; D002633:Chemotaxis; D003198:Computer Simulation; D004926:Escherichia coli / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D008024:Ligands; D008027:Light; D008745:Methylation; D008954:Models, Biological; D012542:Scattering, Radiation; D015398:Signal Transduction; D012984:Software; D014741:Video Recording
chemical_list: D008024:Ligands
keywords: Fourier image analysis; bacterial chemotaxis; collective motion