Bacteriorhodopsin-embedded purple membrane (bR-PM) is one of the most promising biomaterials for various bioelectronics applications. In this work, we demonstrate that a dipole bio-originated from bR-PM can bidirectionally mediate the performance of a bottom-contact TiO(2) nanowire field effect transistor (FET) for performance improvement. When negative gate voltage is applied, both transfer and output characteristics of the TiO(2) nanowire FET are enhanced by the bR-PM modification, resulting in a hole mobility increased by a factor of 2. The effect of the number of the deposited bR-PM layers on the normalized DeltaI(D) of the FET suggests that the additional electric field generated by the dipole moment natively existing in bR-PM actually boosts the performance of the TiO(2) nanowires FET.