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Featured researches published by Shu-Hong Gao.


Environmental Science & Technology | 2013

Accelerated Reduction of Chlorinated Nitroaromatic Antibiotic Chloramphenicol by Biocathode

Bin Liang; Hao-Yi Cheng; Deyong Kong; Shu-Hong Gao; Fei Sun; Dan Cui; Fanying Kong; Aijuan Zhou; Wenzong Liu; Nanqi Ren; Wei-Min Wu; Aijie Wang; Duu-Jong Lee

Chlorinated nitroaromatic antibiotic chloramphenicol (CAP) is a priority pollutant in wastewaters. A fed-batch bioelectrochemical system (BES) with biocathode with applied voltage of 0.5 V (served as extracellular electron donor) and glucose as intracellular electron donor was applied to reduce CAP to amine product (AMCl2). The biocathode BES converted 87.1 ± 4.2% of 32 mg/L CAP in 4 h, and the removal efficiency reached 96.0 ± 0.9% within 24 h. Conversely, the removal efficiency of CAP in BES with an abiotic cathode was only 73.0 ± 3.2% after 24 h. When the biocathode was disconnected (no electrochemical reaction but in the presence of microbial activities), the CAP removal rate was dropped to 62.0% of that with biocathode BES. Acetylation of one hydroxyl of CAP was noted exclusive in the biocatalyzed process, while toxic intermediates, hydroxylamino (HOAM), and nitroso (NO), from CAP reduction were observed only in the abiotic cathode BES. Electrochemical hydrodechlorination and dehalogenase were responsible for dechlorination of AMCl2 to AMCl in abiotic and microbial cathode BES, respectively. The cyclic voltammetry (CV) highlighted higher peak currents and lower overpotentials for CAP reduction at the biocathode compared with abiotic cathode. With the biocathode BES, antibacterial activity of CAP was completely removed and nitro group reduction combined with dechlorination reaction enhanced detoxication efficiency of CAP. The CAP cathodic transformation pathway was proposed based on intermediates analysis. Bacterial community analysis indicated that the dominate bacteria on the biocathode were belonging to α, β, and γ-Proteobacteria. The biocathode BES could serve as a potential treatment process for CAP-containing wastewater.


Water Research | 2016

Evaluating simultaneous chromate and nitrate reduction during microbial denitrification processes.

Lai Peng; Yiwen Liu; Shu-Hong Gao; Xueming Chen; Bing-Jie Ni

Sulfur-based autotrophic denitrification and heterotrophic denitrification have been demonstrated to be promising technological processes for simultaneous removal of nitrate NO3(-) and chromate (Cr (VI)), two common contaminants in surface and ground waters. In this work, a mathematical model was developed to describe and evaluate the microbial and substrate interactions among sulfur oxidizing denitrifying organism, methanol-based heterotrophic denitrifiers and chromate reducing bacteria in the biofilm systems for simultaneous nitrate and chromate removal. The concomitant multiple chromate reduction pathways by these microbes were taken into account in this model. The validity of the model was tested using experimental data from three independent biofilm reactors under autotrophic, heterotrophic and mixotrophic conditions. The model sufficiently described the nitrate, chromate, methanol, and sulfate dynamics under varying conditions. The modeling results demonstrated the coexistence of sulfur-oxidizing denitrifying bacteria and heterotrophic denitrifying bacteria in the biofilm under mixotrophic conditions, with chromate reducing bacteria being outcompeted. The sulfur-oxidizing denitrifying bacteria substantially contributed to both nitrate and chromate reductions although heterotrophic denitrifying bacteria dominated in the biofilm. The mixotrophic denitrification could improve the tolerance of autotrophic denitrifying bacteria to Cr (VI) toxicity. Furthermore, HRT would play an important role in affecting the microbial distribution and system performance, with HRT of higher than 0.15 day being critical for a high level removal of nitrate and chromate (over 90%).


Scientific Reports | 2015

Evaluation on the nanoscale zero valent iron based microbial denitrification for nitrate removal from groundwater

Lai Peng; Yiwen Liu; Shu-Hong Gao; Xueming Chen; Pei Xin; Xiaohu Dai; Bing-Jie Ni

Nanoscale zero valent iron (NZVI) based microbial denitrification has been demonstrated to be a promising technology for nitrate removal from groundwater. In this work, a mathematical model is developed to evaluate the performance of this new technology and to provide insights into the chemical and microbial interactions in the system in terms of nitrate reduction, ammonium accumulation and hydrogen turnover. The developed model integrates NZVI-based abiotic reduction of nitrate, NZVI corrosion for hydrogen production and hydrogen-based microbial denitrification and satisfactorily describes all of the nitrate and ammonium dynamics from two systems with highly different conditions. The high NZVI corrosion rate revealed by the model indicates the high reaction rate of NZVI with water due to their large specific surface area and high surface reactivity, leading to an effective microbial nitrate reduction by utilizing the produced hydrogen. The simulation results further suggest a NZVI dosing strategy (3–6 mmol/L in temperature range of 30–40 °C, 6–10 mmol/L in temperature range of 15–30 °C and 10–14 mmol/L in temperature range of 5–15 °C) during groundwater remediation to make sure a low ammonium yield and a high nitrogen removal efficiency.


Environmental Science & Technology | 2016

Determining multiple responses of Pseudomonas aeruginosa PAO1 to an antimicrobial agent, free nitrous acid

Shu-Hong Gao; Lai Fan; Lai Peng; Jianhua Guo; Míriam Agullo-Barcelo; Zhiguo Yuan; Philip L. Bond

Free nitrous acid (FNA) has recently been demonstrated as an antimicrobial agent on a range of micro-organisms, especially in wastewater-treatment systems. However, the antimicrobial mechanism of FNA is largely unknown. Here, we report that the antimicrobial effects of FNA are multitargeted. The response of a model denitrifier, Pseudomnas aeruginosa PAO1 (PAO1), common in wastewater treatment, was investigated in the absence and presence of inhibitory level of FNA (0.1 mg N/L) under anaerobic denitrifying conditions. This was achieved through coupling gene expression analysis, by RNA sequencing, and with a suite of physiological analyses. Various transcripts exhibited significant changes in abundance in the presence of FNA. Respiration was likely inhibited because denitrification activity was severely depleted, and decreased transcript levels of most denitrification genes occurred. As a consequence, the tricarboxylic acid (TCA) cycle was inhibited due to the lowered cellular redox state in the FNA-exposed cultures. Meanwhile, during FNA exposure, PAO1 rerouted its carbon metabolic pathway from the TCA cycle to pyruvate fermentation with acetate as the end product as a possible survival mechanism. Additionally, protein synthesis was significantly decreased, and ribosome preservation was evident. These findings improve our understanding of PAO1 in response to FNA and contribute toward the potential application for use of FNA as an antimicrobial agent.


Chemosphere | 2015

Assessing chromate reduction by dissimilatory iron reducing bacteria using mathematical modeling

Lai Peng; Yiwen Liu; Shu-Hong Gao; Xiaohu Dai; Bing-Jie Ni

Chromate (Cr (VI)) is a ubiquitous contaminant in aquifers and soils, which can be reduced to its trivalent counterpart (Cr (III)), with the hazard being relieved. The coupling microbial and chemical reduction by dissimilatory iron reducing bacteria (IRB) is a promising approach for the reduction of Cr (VI) to Cr (III). In this work, three mathematical models with different Cr (VI) reduction pathways were proposed and compared based on their ability to predict the performance of an IRB-based stirred-flow reactor treating Cr (VI) contaminated medium and to provide insights into the possible chemical or microbial pathways for Cr (VI) reduction in the system. The Cr (VI) reduction was considered as chemical reaction between Fe (II) and Cr (VI), direct microbial reduction by IRB and combined biotic-abiotic reduction in these three models, respectively. Model evaluation results indicated that the model incorporating both chemical and microbial Cr (VI) reductions could well describe the system performance. In contrast, the other two single-pathway models were not capable of predicting the experimental data, suggesting that both chemical and microbial pathways contributed to Cr (VI) reduction by IRB. The validity of the two-pathway model was further confirmed by an independent experimental data set with different conditions. The results further revealed that the organic carbon availability and Cr (VI) loading rates for the IRB in the system determined the relative contributions of chemical and microbial pathways to overall Cr (VI) reduction.


ACS Applied Materials & Interfaces | 2017

Copper oxide nanoparticles induce lysogenic bacteriophage and metal-resistance genes in pseudomonas aeruginosa PAO1

Jianhua Guo; Shu-Hong Gao; Ji Lu; Philip L. Bond; Willy Verstraete; Zhiguo Yuan

The intensive use of metal-based nanoparticles results in their continuous release into the environment, leading to potential risks for human health and microbial ecosystems. Although previous studies have indicated that nanoparticles may be toxic to microorganisms, there is a scarcity of data available to assess the underlying molecular mechanisms of inhibitory and biocidal effects of nanoparticles on microorganisms. This study used physiological experiments, microscopy, live/dead staining, and the genome-wide RNA sequencing to investigate the multiple responses of Pseudomonas aeruginosa to the exposure of copper oxide nanoparticles (CuO NPs). The results for the first time show that CuO NPs induce lysogenic bacteriophage, which might render defective within a bacterial host. The presence of CuO NPs causes nitrite accumulation and great increases in N2O emissions. Respiration is likely inhibited as denitrification activity is depleted in terms of decreased transcript levels of most denitrification genes. Meanwhile, CuO NPs exposure significantly up-regulated gene expression for those coding for copper resistance, resistance-nodulation-division, P-type ATPase efflux, and cation diffusion facilitator transporters. Our findings offer insights into the interaction between environmental bacteria and CuO NPs at the transcriptional level and, thus, improve our understanding of potential risks of nanoparticles on microbial ecosystems and public health.


Applied and Environmental Microbiology | 2016

Antimicrobial effects of free nitrous acid on Desulfovibrio vulgaris: implications for sulfide-induced corrosion of concrete

Shu-Hong Gao; Jun Yuan Ho; Lu Fan; David J. Richardson; Zhiguo Yuan; Philip L. Bond

ABSTRACT Hydrogen sulfide produced by sulfate-reducing bacteria (SRB) in sewers causes odor problems and asset deterioration due to the sulfide-induced concrete corrosion. Free nitrous acid (FNA) was recently demonstrated as a promising antimicrobial agent to alleviate hydrogen sulfide production in sewers. However, details of the antimicrobial mechanisms of FNA are largely unknown. Here, we report the multiple-targeted antimicrobial effects of FNA on the SRB Desulfovibrio vulgaris Hildenborough by determining the growth, physiological, and gene expression responses to FNA exposure. The activities of growth, respiration, and ATP generation were inhibited when exposed to FNA. These changes were reflected in the transcript levels detected during exposure. The removal of FNA was evident by nitrite reduction that likely involved nitrite reductase and the poorly characterized hybrid cluster protein, and the genes coding for these proteins were highly expressed. During FNA exposure, lowered ribosome activity and protein production were detected. Additionally, conditions within the cells were more oxidizing, and there was evidence of oxidative stress. Based on an interpretation of the measured responses, we present a model depicting the antimicrobial effects of FNA on D. vulgaris. These findings provide new insight for understanding the responses of D. vulgaris to FNA and will provide a foundation for optimal application of this antimicrobial agent for improved control of sewer corrosion and odor management. IMPORTANCE Hydrogen sulfide produced by SRB in sewers causes odor problems and results in serious deterioration of sewer assets that requires very costly and demanding rehabilitation. Currently, there is successful application of the antimicrobial agent free nitrous acid (FNA), the protonated form of nitrite, for the control of sulfide levels in sewers (G. Jiang et al., Water Res 47:4331–4339, 2013, http://dx.doi.org/10.1016/j.watres.2013.05.024). However, the details of the antimicrobial mechanisms of FNA are largely unknown. In this study, we identified the key responses (decreased anaerobic respiration, reducing FNA, combating oxidative stress, and shutting down protein synthesis) of Desulfovibrio vulgaris Hildenborough, a model sewer corrosion bacterium, to FNA exposure by examining the growth, physiological, and gene expression changes. These findings provide new insight and underpinning knowledge for understanding the responses of D. vulgaris to FNA exposure, thereby benefiting the practical application of FNA for improved control of sewer corrosion and odor.


Environmental Science: Water Research & Technology | 2015

Mathematical modeling of microbial extracellular electron transfer by electrically active microorganisms

Yiwen Liu; Lai Peng; Shu-Hong Gao; Xiaohu Dai; Bing-Jie Ni

Extracellular electron transfer by electrically active microorganisms enables the conduction of electrons over long spatial distances in marine sediment, which plays an important role in global biogeochemical cycles through the generated electric currents. In this study, a mathematical model is developed to describe the extracellular electron transfer process by electrically active microorganisms through decoupling the oxidation and reduction processes, taking sulfide-oxidizing bacteria as examples. In this model, extracellular electron carriers are introduced as new components to link the oxidation and reduction reactions and to achieve the long-range indirect electron transport using decoupled Monod kinetics, allowing for the description of distinct separation of contrasting electrochemical regions. The developed model has been successfully applied to reproduce experimental data for sulfide oxidation and electron acceptor reduction via extracellular electron transfer from two independent study reports with different experimental conditions (oxygen or nitrate as electron acceptors) and transfer mechanisms (possibly different extracellular electron carriers) through calibration of three key parameters (koxi, kred and Kmed) that govern the long-range indirect electron transport. The model satisfactorily describes the experimental data from both systems, suggesting the validity and applicability of the model. Modeling results clearly showed two distinct zones with sulfide consumption (sediment floor) and oxygen (or nitrate) reduction (top surface) enabled by electron conduction via electron carriers. The model of this work would enhance our understanding of biogeochemical interactions with natural electric currents allowing oxidation and reduction processes to be spatially separated yet instantly and intimately coupled, while also potentially being applicable to a wide range of electrically active microorganisms.


International Biodeterioration & Biodegradation | 2016

Bioelectrochemical reduction of an azo dye by a Shewanella oneidensis MR-1 formed biocathode

Shu-Hong Gao; Lai Peng; Yiwen Liu; Xu Zhou; Bing-Jie Ni; Philip L. Bond; Bin Liang; Aijie Wang


Journal of Membrane Science | 2015

Biodegradation of pharmaceuticals in membrane aerated biofilm reactor for autotrophic nitrogen removal: A model-based evaluation

Lai Peng; Xueming Chen; Yifeng Xu; Yiwen Liu; Shu-Hong Gao; Bing-Jie Ni

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Philip L. Bond

University of Queensland

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Zhiguo Yuan

University of Queensland

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Jianhua Guo

University of Queensland

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Xueming Chen

University of Queensland

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Ji Lu

University of Queensland

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Lu Fan

University of Queensland

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Aijie Wang

Chinese Academy of Sciences

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Bin Liang

Chinese Academy of Sciences

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