Chemotaxis of ciliated microorganisms: with and without noise

Abstract

Biological systems like ciliated microorganisms are capable to respond to the external chemical gradients, a process known as chemotaxis which has been studied here using the chiral squirmer model. This theoretical model considers the microorganism as a spherical body with an active surface slip velocity. In presence of a chemical gradient, the internal signaling network of the microorganism is triggered due to binding of the ligand with the receptors on the surface of the body. Consequently, the coefficients of the slip velocity get modified resulting in a change in the path followed by the body. We observe that the strength of the gradient is not the only parameter which controls the dynamics of the body but also the adaptation time play a very significant role in the success of chemotaxis of the body. Path of the body is smooth if we ignore the discreteness in the ligand-receptor binding which is stochastic in nature. In presence of the later, the path is not only irregular but the dynamics of the body changes. We calculate the mean first passage time, by varying strength of the chemical gradient and adaptation time, to investigate the success rate of chemotaxis.