Atrazine-degrading bacteria for bioremediation strategy: A review

Research on atrazine has expanded over the past decade. Studies focussing on the adverse effects of atrazine, methods for atrazine removal, and evaluation of water quality have been conducted. Atrazine is a major concern as it is a predominant herbicide identified in soil and water due to its long half-life, moderate persistent, high mobility, and solubility that can be influenced by many factors. This review focuses on the most recent bacteria capable of degrading atrazine, the gene involved in the degradation, the degradation mechanism, and the bioremediation alternative for atrazine degradation. The advantages and disadvantages of each approach are also presented. In short, atrazine-degrading bacteria produce enzymes to break down atrazine (i.e. atrazine chlorohydrolase, hydroxyatrazine hydrolase, N-isopropylammelide amidohydrolase, cyanuric acid amidohydrolase, 1-carboxybiuret amidohydrolase, allophanate amidohydrolase, and triazine hydrolase) and enhance metabolic mechanisms. Among the most isolated atrazine-degrading bacteria from 2014 to 2021, only Arthrobacter sp. FM326, Pseudomonas sp. AACB, and Bacillus subtilis HB-6 are capable of fully degrading atrazine into carbon dioxide and ammonia. The atrazine catabolic pathway is best described in Pseudomonas sp. strain ADP that encodes atrazine-degrading genes on a single conjugative pADP1 plasmid along with transposase sequences and insertion elements. However, the enzymatic mechanisms and the role of atrazine-degrading genes during degradation need to be further clarified. It is assumed that the bacteria with complete sets of atrazine-degrading genes will fully degrade atrazine, but Arthrobacter sp. FM326 can completely degrade atrazine with only three sets of atrazine-degrading genes.