Cellular Influence Of MC-LR On Pseudomonas Putida

Microcystin-LR(MC-LR)is a secondary metabolite from eutrophication, which is highly biotoxic. To reveal the toxicity of MC-LR on microorganisms, the effect of MC-LR on cell surface characteristics, cellular viability, metabolism, regulation ability and morphology of Pseudomonas putida was investigated in current study.Cytoplasmic membrane permeability of P. putida changed under different concentrations of MC-LR, and higher concentrations of MC-LR caused the membrane permeability continued to increase. P. putida cells ruptured under 2.5 mg·L-1 MC-LR, which led to loss of cellular integrity, outflow of intracellular materials, and affected the distribution of ions inside/outside the cells. Depolarization happened and cell membrane potential decreased.MC-LR can affect bioactivity of P. putida and accelerate the death of bacterial cells. Biolog experiment suggested that the utilization of carbon sources of P. putida after MC-LR treatment was obviously lower than that of the control group. The toxicity of MC-LR apparently weakened the metabolic activity of P. putida. The flow cytometry experiment showed that the viability of bacterial cells decreased and apoptosis occurred under the stress of MC-LR. Moreover, the death rate rose up with the increase of MC-LR concentration. Compared with the control, the death rate at day 5 was increased by nearly 30% when 2.5 mg·L-1 MC-LR was added, and the biomass in the system kept decreasing with time.MC-LR can influence the ion metabolism and soluble protein secreted by P. putida. The soluble sugar and Na+、Cl- release increased with the rising concentration of MC-LR ranging from 0 mg·L-1 to 2.5 mg·L-1. the SOD and ATPase analyses suggested that low level of MC-LR induced higher enzyme activity while higher concentration of MC-LR damaged the antioxidation and metabolic activity of P. putida, which caused ROS accumulation inside the cells and suppressed the SOD and ATPase, making the enzyme activity continuously decrease.Scanning electron microscope(SEM) analysis showed that the cells were deformed under the toxicity of MC-LR. After 5 day exposure, 2.5 mg·L-1 MC-LR caused mass mortality of P. putida. The intracellular materials flowed out and the cells were severely damaged. SEM also verified the toxicity of MC-LR on P. putida, and the cells damages were more serious with longer contact time with higher concentration of MC-LR.