Bioremediation of perchlorate-cotaminated water by a heterotrophic perchlorate reducing bacterium creates a multiple electron acceptor-donor system. We experimentally determined the perchlorate reduction by Azospira sp. KJ at multiple pH, electron acceptors and donors systems; this was the aim of this study. Perchlorate reduction was drastically inhibited at the pH 6.0, and the maximum reduction of perchlorate by Azospira sp. KJ was observed at pH value of 8.0. Perchlorate reduction was retarded in ClO4---ClO3-, ClO4--ClO3--NO3-,and ClO4--NO3- acceptor systems, while being completely inhibited by the additional O-2 in the ClO4--O-2 acceptor system. The reduction proceeded as an order of ClO3-, ClO4-, and NO3- in the ClO4--ClO3--NO3- system. K-s, v(max,) and q(max) obtained at different e(-) acceptor and donor conditions are calculated as 140.5-190.6 mg/L, 8.7-13.2 mg-perchlorate/L-h, and 0.094-0.16 mg-perchlorate/mg-DW-h, respectively. (C) 2014 Elsevier B.V. All rights reserved.