Project description: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.
Project description:Bacterial anaerobic respiration using extracellular electron acceptor plays a predominant role in global biogeochemical cycles. However, the bacterial adaptive mechanisms to the toxic organic pollutant as the extracellular electron acceptor during anaerobic respiration is not clear, which limits us to optimize the strategies for the bioremediation of contaminated environment. Here, we report the physiological characteristics and the global gene expression of an ecologically successful bacterium Shewanella decolorationis S12 when using a typical toxic organic pollutant, amaranth, as the extracellular electron acceptor. Our results revealed that filamentous shift (the cells stretched to fiber-like shapes as long as 18 μm) occurred under amaranth stress. Persistent stress led to higher filamentous cell rate and decolorization ability in subcultural cells compared with parental strains. Additionally, the expression of genes involved in cell division, chemotaxi system, energy conservation, damage repair, and material transport in filamentous cells were significantly stimulated. The detailed roles of some genes with significantly elevated expressions in filamentous cells were identified by site-directed mutagenesis, such as the outer membrane porin genes ompA and ompW, the cytochrome C genes arpC and arpD, the global regulatory factor gene rpoS and methyl-accepting chemotaxis proteins genes SHD_2793 and SHD_0015. Finally, a conceptual model was proposed to help deepen our insights into both the bacterial survival strategy when toxic organics were present, and the mechanisms in which these toxic organics were biodegraded as the extracellular electron acceptors.
