4-nitroaniline (4-NA) is one of the major priority pollutants generated from industrial productions and pesticide transformation; however very limited biodegradation details have been reported. This work is the first to report 4-NA biodegradation kinetics and toxicity reduction using a newly isolated plant-growth promoting bacterium, Acinetobacter sp. AVLB2. The 4-NA-dependent growth kinetics parameters: mu(max), K-s and K-i, were determined to be 0.039 h(-1), 6.623 mg L-1 and 25.57 mg L-1, respectively using Haldane inhibition model, while the maximum biodegradation rate (V-max) of 4-NA was at 0.541 mg L-1 h(-1). and 0.551 mg L-1 h(-1), following Michaelis-Menten and Hanes-Woolf models, respectively. Biodegradation pathway of 4-NA by Acinetobacter sp. AVLB2 was proposed, and successfully led to the reduction of 4-NA toxicity according to the following toxicity assessments: microbial toxicity using Escherichia coli DH5 alpha, phytotoxicity with Vigna radiata and Crotalaria juncea, and cytogenotoxicity with Album cepa root-tip cells. In addition, Acinetobacter sp. AVLB2 possess important plant-growth promoting traits, both in the presence and absence of 4-NA. This study has provided a new insight into 4-NA biodegradation ability and concurrent plant-growth promoting activities of Acinetobacter sp. AVLB2, which may indicate its potential role for rhizoremediation, while sustaining crop production even under 4-NA stressed environment. (C) 2015 Elsevier B.V. All rights reserved.