  The properties of the D-brane fluctuations are investigated using the two
types of deformation of the Dirac structure, based on the B-transformation and
the beta-transformation, respectively. The former gives the standard gauge
theory with 2-form field strength. The latter gives a non-standard gauge theory
on the Poisson manifold with bivector field strength and the vector field as a
gauge potential, where the gauge symmetry is a diffeomorphism generated by the
Hamiltonian vector field. The map between the two gauge theories is also
constructed with the help of Moser's Lemma and the Magnus expansion. We also
investigate the relation to the gauge theory on the noncommutative D-branes.
