title: Antioxidative responses of Pseudomonas fluorescens YZ2 to simultaneous exposure of Zn and Cefradine.
abstract: Binary pollution of both heavy metals and antibiotics has received increasing attentions for their joint effects of eco-toxicity and health hazards. To reveal the effects of mixtures of different pollutants on bacterial antioxidant response system, Pseudomonas fluorescens ZY2, a new strain isolated from swine wastewater, was chosen to determinate growth (bacterial density OD600), reactive oxygen species (ROS) concentration, protein concentration and superoxide dismutase (SOD) activity under exposure treatments of Zn, Cefradine or Zn + Cefradine. Bacterial densities of all the treatment groups increased significantly over the incubation time, but those containing pollutant addition were slightly lower than the control at different times of incubation. Both ROS concentration and SOD activity increased first and then decreased (p < 0.01) over time, which was opposite to the protein concentrations (p < 0.01), showing a much significant increase by Cefradine alone. With Zn concentration increasing from 40 to 160 mg/L, the intracellular SOD activity increased as a response to the improvement of ROS (p < 0.05), while the balance between ROS and SOD was broken down due to the disproportionate change of total SOD activity and ROS concentration, the bacterial densities therefore decreased for the weak resistance. With the combined treatment of Zn (200 mg/L) and Cefradine (1 mg/L), though the toxicity of Zn caused a much significant increase of ROS, the bacterial resistance was further improved showing a more significant increase of total SOD activity and the bacterial densities therefore increased bacterial growth. Zn concentration also affected the protein synthesis. Either single or binary stress induced the bacterial resistance by regulating SOD activity to eliminate ROS. All results of the bacterial oxidant stress, SOD response and protein synthesis in the combined treatment groups were more complicated than those in single treatment groups, which depended on the properties of the single treatment as well as the interaction between the two treatments upon bacterial activity. For P. fluorescens ZY2, the mediation of SOD activity to eliminate ROS in response to the combined exposure to Zn and Cefradine was first revealed as one of the co-resistance mechanisms, which is informative to further understanding the risk of antibiotics resistant bacteria to human and environmental health more accurately.
authors.affiliation: School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, People's Republic of China. hopeybxu@163.com.|College of Environmental Science and Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China. hopeybxu@163.com.|State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, 510641, People's Republic of China. hopeybxu@163.com.|Key Laboratory of Environmental Protection and Eco-remediation of Guangdong Regular Higher Education Institutions, Guangzhou Higher Education Mega Center, South China University of Technology, Guangzhou, 510006, People's Republic of China. hopeybxu@163.com.
authors.forename: Yan-Bin
authors.initials: YB
authors.lastname: Xu
authors.affiliation: School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Jia-Xin
authors.initials: JX
authors.lastname: Xu
authors.affiliation: School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Jin-Liang
authors.initials: JL
authors.lastname: Chen
authors.affiliation: School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Huang
authors.affiliation: College of Environmental Science and Engineering, South China University of Technology, Guangzhou, 510006, People's Republic of China. fesqzhou@scut.edu.cn.|State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, 510641, People's Republic of China. fesqzhou@scut.edu.cn.|Key Laboratory of Environmental Protection and Eco-remediation of Guangdong Regular Higher Education Institutions, Guangzhou Higher Education Mega Center, South China University of Technology, Guangzhou, 510006, People's Republic of China. fesqzhou@scut.edu.cn.|Guizhou Academy of Sciences, Shanxi Road 1#, Guiyang, 550001, People's Republic of China. fesqzhou@scut.edu.cn.
authors.forename: Shao-Qi
authors.initials: SQ
authors.lastname: Zhou
authors.affiliation: School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Wen
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000975:Antioxidants / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002515:Cephradine / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D011551:Pseudomonas fluorescens / Q000187:drug effects* / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D034421:Sus scrofa; D062065:Wastewater; D015032:Zinc / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D000975:Antioxidants; D001426:Bacterial Proteins; D002515:Cephradine; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase; D062065:Wastewater; D015032:Zinc
keywords: Antioxidant; Cefradine; Protein; Reactive oxygen species (ROS); Resistance; Superoxide dismutase (SOD); Zn