  It is known that many constructions arising in the classical Gaussian
infinite dimensional analysis can be extended to the case of more general
measures. One such extension can be obtained through biorthogonal systems of
Appell polynomials and generalized functions. In this paper, we consider linear
continuous operators from a nuclear Frechet space of test functions to itself
in this more general setting. We construct an isometric integral transform
(biorthogonal CS-transform) of those operators into the space of germs of
holomorphic functions on a locally convex infinite dimensional nuclear space.
Using such transform, we provide characterization theorems and give
biorthogonal chaos expansion for operators.
