Response of Pseudomonas putida cells to MC-LR stress
DENG Ting-jin1, YIN Hua1, YE Jin-shao2, PENG Hui3, LIU Zhi-chen1
1. Key Laboratory on Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education College of Environment and Energy, South China University of Technology, Guangzhou 510006, China;
2. College of Environment, Jinan University, Guangzhou 510632, China;
3. Department of Chemistry, Jinan University, Guangzhou 510632, China
The cell integrity and biomass changes of Pseudomonas putida, a MC-LR degrading bacterium, were studied by inoculating 1.0g/L bacterium into systems with different concentrations of MC-LR. The oxidative stress of MC-LR on bacterial cell and the responses of antioxidase were also investigated. The results showed that membrane permeability of P. putida increased under the influence of MC-LR, causing membrane damage, which resulted in the outflow of intracellular substances and the destruction of cell integrity. Also, MC-LR could induce the oxidative stress on the cells of P. putida. With prolonged exposure to MC-LR, reactive oxygen species (ROS) and malondialdehyde (MDA), a product of membrane lipid peroxidation, evidently accumulated in the system, and had obvious dose-effect relationship. Under the effect of MC-LR, the activity of superoxide dismutase (SOD) increased first and then declined, exhibiting an active response to MC-LR of low level. However, after contacting higher concentrations (2.5 mg/L) of MC-LR for 5d, ROS accumulation was so high as to cause damage to the metabolism of cells. As a result, SOD activity was suppressed and cells suffered mass mortality, and the biomass decreased by 50% compared with the control.
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