Molecular mechanism of zero valent iron-enhanced microbial azo reduction in Shewanella decolorationis S12

Here, we established a successive Fe0-enhanced microbe system to remove azo dye (a typical organic pollutant) by Shewanella decolorationis S12 (S. decolorationis S12, an effective azo dye degradation bacterium) and examined the gene expression time course (10, 30, 60, and 120 min) in whole genome transcriptional level. Comparing with the treatment without ZVI, approximately 8% genes affiliated with 10 different gene expression profiles in S. decolorationis S12 were significantly changed in 120 min during the ZVI-enhanced microbial azo reduction. Intriguingly, MarR transcriptional factor might play a vital role in regulating ZVI-enhanced azo reduction in the aspect of energy production, iron homeostasis, and detoxification. Further investigation showed that induced [Ni-Fe] H2ase genes (hyaABCDEF) and azoreductase genes (mtrABC-omcA) contributed to ZVI-enhanced energy production, while reduced iron uptake (hmuVCB and feoAB), induced sulfate assimilation (cysPTWA) and cysteine biosynthesis (cysM) related genes were essential to iron homeostasis and detoxification. This study disentangles underlying mechanisms of ZVI-enhanced azo reduction in S. decolorationis S12 and lays a foundation for further optimization of integrated ZVI-microbial system for efficient organic pollution treatment. mRNA profiles of Shewanella decoloriationis S12 treated/untreated with Fe0 for 10, 30, 60, and 120 min were generated by deep sequencing, in triplicate, using Illumina Hiseq 2000.

本研究构建了一套零价铁（Fe0）强化型微生物体系，利用脱色希瓦氏菌S12（Shewanella decolorationis S12，一种高效偶氮染料（azo dye）降解菌株）去除偶氮染料这类典型有机污染物，并在全基因组转录水平上检测了该体系的基因表达时序变化，采样时间点设置为10、30、60和120分钟。与未添加零价铁（ZVI）的对照组相比，在零价铁强化微生物偶氮还原过程的120分钟时，脱色希瓦氏菌S12中隶属于10种不同基因表达谱的约8%基因发生了显著表达变化。值得注意的是，MarR转录因子（MarR transcriptional factor）可能在调控零价铁强化偶氮还原的过程中，于能量产生、铁稳态与解毒这几个维度发挥关键作用。进一步研究显示，被诱导表达的[镍铁]氢化酶（[Ni-Fe] H2ase）基因（hyaABCDEF）与偶氮还原酶（azoreductase）基因（mtrABC-omcA）可促进零价铁强化的能量产生过程；而铁摄取相关基因（hmuVCB与feoAB）的表达下调，以及硫酸盐同化（cysPTWA）与半胱氨酸生物合成（cysM）相关基因的诱导表达，则对铁稳态维持与解毒过程至关重要。本研究阐明了脱色希瓦氏菌S12中零价铁强化偶氮还原的潜在分子机制，为进一步优化集成零价铁-微生物体系以实现高效有机污染治理奠定了坚实基础。本研究采用Illumina Hiseq 2000平台，对经零价铁处理与未处理的脱色希瓦氏菌S12，分别在10、30、60和120分钟时的mRNA表达谱进行了三次生物学重复的深度测序。