Abstract

Many bacteria swim chemotactically: they navigate up chemical gradients. The biophysics of chemotaxis in liquids is well understood. Its study in porous media, however, has recently revealed unexpected surprises. Existing models describe chemotactic migration in porous media as if bacteria were gas particles in an external field. But this description, which maps onto ordinary statistical physics (with detailed balance), fails to describe the migration of E. coli bacteria in porous gels. A new transport theory, with chemotactic memory (and without detailed balance), is required to account for the observed suppression of chemotaxis in dense gels.

This finding has practical implications for attempts to use chemotactic bacteria to clean up soil (bioremediation). It is part of growing evidence that a new biological statistical physics needs to be developed to accurately describe populations of swimming, environment-sensing microorganisms.

My talk will be in two parts. In the first (slides) I will motivate the topic, describe my experimental work on bacterial migration in agar gels and outline the theory. In the second (at the board) I will sketch the stat mech derivation of transport paramaters in porous media accounting for chemotactic memory.