Technology developed at IP2I allows bacteria motions to be observed with very high precision

The first steps in pathogenic spread into a host and colonization of an environment by motile bacteria involve that they swim near a surface. Researchers from the Institute of Physics of the 2 Infinites of Lyon, the Laboratory of Geology of Lyon: Earth, planets and environment and the Laboratory of Physics have designed an experiment to describe the movement of E. Coli at very high resolution and high frequency near a surface.

This work shows that, against all odds, microorganisms that are trapped near surfaces can get rid of this fatality by suddenly reorienting themselves and thereby exploring a larger environment.In a liquid medium, a bacterial population is able to move towards conditions which are more favorable to it.

To do this, each bacteria follows a "random walk", made up of portions of straight paths and very brief reorientation events whose frequency it biases. When an E. coli bacterium approaches a surface, hydrodynamics forces it to adopt a circular trajectory a few hundred nanometers above the surface. The bacteria are trapped.

But is it so constrained as this in this critical stage for the infection and colonization of new environments?
To answer this question, a team of researchers specializing in the development of IP2I sensors and researchers working on the swimming of bacteria on the surfaces of the Laboratory of Physics and the Laboratory of Geology of Lyon have combined their competences.

By breaking down the body movement sequence of the E. coli model bacteria at very high frequency (500 Hz) over long periods (2 s), we observe that the bacteria makes very short swimming pauses (100 ms). During these intervals, the body is reoriented, but sometimes its resulting reorientation is very small, sometimes it is extremely important. Thus, this erratic behavior unexpectedly allows bacteria trapped near a surface to get rid of this fatality by suddenly reorienting itself. Bacteria can then explore a larger environment.

Link to the paper here.