Transcriptome profiling of Pseudomonas aeruginosa YH reveals mechanisms of 2, 2′, 4, 4′-tetrabrominated diphenyl ether tolerance and biotransformation

Abstract

Aerobic degradation of 2, 2′, 4, 4′-tetrabrominated diphenyl ether (BDE-47) by Pseudomonas aeruginosa YH (P. aeruginosa YH) were investigated in this study. BDE-47 degradation was mainly through the biological action of intracellular enzymes, and the metabolites included debrominated metabolites (BDE-28 and BDE-7), hydroxylated metabolites (6-OH-BDE-47, 5-OH-BDE-47, 2′-OH-BDE-28 and 4′-OH-BDE-17), and brominated phenols (2,4-DBP and 4-BP). P. aeruginosa YH also exhibited exceptional ability to degrade intermediates, and the degradation rates of 50 μg/L BDE-28, BDE-7, and 2,4-DBP were 68.4%, 82.3% and 92.7% on the 5th day, separately. Transcriptome sequencing revealed that 991 genes were up-regulated, and 923 genes were down-regulated in P. aeruginosa YH after exposure to 0.5 mg/L BDE-47 (FDR ≤ 0.001, |log2Ratio| ≥ 1). The differentially expressed genes were related to transport, metabolism and stress response. Harf inhibitory concentration (IC50) of BDE-47 decreased from 167.5 mg/L to 68.4 mg/L when multidrug efflux pump was inactivated by 20 mg/L andrographolide, indicating that it helped the bacterial tolerance against BDE-47. Moreover, efflux pump inhibition would accelerate the adsorption of BDE-47. The adsorption rate obtained equilibrium at approximately 70% in 2 days, while 5 days in the control group. Degradation efficiency of 2 mg/L BDE-47 decreased from 26.8% to 13.9% when multidrug efflux was suppressed.