  Chemotaxis describes the movement of an organism, such as single or
multi-cellular organisms and bacteria, in response to a chemical stimulus. Two
widely used models to describe the phenomenon are the celebrated Keller-Segel
equation and a chemotaxis kinetic equation. These two equations describe the
organism movement at the macro- and mesoscopic level respectively, and are
asymptotically equivalent in the parabolic regime. How the organism responds to
a chemical stimulus is embedded in the diffusion/advection coefficients of the
Keller-Segel equation or the turning kernel of the chemotaxis kinetic equation.
Experiments are conducted to measure the time dynamics of the organisms'
population level movement when reacting to certain stimulation. From this one
infers the chemotaxis response, which constitutes an inverse problem. \\ In
this paper we discuss the relation between both the macro- and mesoscopic
inverse problems, each of which is associated to two different forward models.
The discussion is presented in the Bayesian framework, where the posterior
distribution of the turning kernel of the organism population is sought after.
We prove the asymptotic equivalence of the two posterior distributions.
