  In gauge theory, the Faddeev-Mickelsson-Shatashvili anomaly arises as a
prolongation problem for the action of the gauge group on a bundle of
projective Fock spaces. In this paper, we study this anomaly from the point of
view of bundle gerbes and give several equivalent descriptions of the
obstruction. These include lifting bundle gerbes with non-trivial structure
group bundle and bundle gerbes related to the caloron correspondence.
