Non-local hydrodynamics of swimming bacteria and self-activated process

Publication Type:

Book Chapters


BIOMAT 2015 Proceedings of the International Symposium on Mathematical and Computational Biology. World Scientific, p.153-165 (2016)



<p>Water fluidity is modified, in a nontrivial manner, by the presence of bacteria above a threshold number density. Under such threshold conditions swimming bacterial suspensions impose a coordinated water movement on a length scale of the order (10–100) micrometers compared with a bacterial size of the order of 3 micrometers. This observation leads to fundamental questions concerning the cell-to-cell communication presently known as quorum sensing. The aim of this paper is to study the quorum state using non-local hydrodynamics. We emphasize that densely packed bacteria may be viewed as ‘bacterial fluid’ or ‘living fluid’ similar to that of dense granular systems. The <span data-scayt_word="behaviour" data-scaytid="1">behaviour</span> of the fluid of granular mass is quite different from that of typical fluids. This granularity imposes a second source of fluctuations because grains cannot be treated as points at any length scale. This type of fluctuation is known as non-local noise in contrast to local noise in usual hydrodynamic flow. The non-local <span data-scayt_word="hydrodynamical" data-scaytid="2">hydrodynamical</span> framework is applied here to consider the effect of non-local noise. In this framework of nonlocal hydrodynamics viscosity is generated by self-induced noise. This viscosity leads the actively moving bacteria into the meta-stable states required to support quorum, given the non-local nature of stresses mediated by <span data-scayt_word="autoinducers" data-scaytid="3">autoinducers</span>. The shear stress created non-locally within this framework depending on the non-local noise of granularity and the viscosity associated to the this noise can be tested experimentally. The existence of this kind non-chemical self-induced process may be present not only in cell-to-cell bacteria communication but also in eukaryotic cell-to-cell interactions.</p>