Investigation of some biochemical parameters of citrobacter freundii exposed to HEAVY metal

In this study, Citrobacter freundii (C. freundii) was grown in an LB medium containing various concentrations of cadmium, vitamin C and selenium. The density of the bacteria in the medium, the concentration of total protein and enzyme activities were determined by spectrophotometer and the level of stress biomarkers and amino acids were determined by high performance liquid chromatography (HPLC). The bacteria were grown at 0, 10, 20, 40, 60, 75, 100 and 125 ppm cadmium (Cd). The groups containing 75, 100 and 125 ppm Cd had a statistically significant decrease in bacterial density (p<0.05). Likewise, a significant increase was observed in the concentration of the bacteria after adding vitamin C (25, 50 and 75 ppm) and selenium (1.0 and 3.0 ppm) to the medium containing 75, 100 and 125 ppm Cd (p <0.05). The groups containing 20, 40, 60, 75, 100 and 125 ppm Cd showed a decreased level of fat and water-soluble vitamins. Addition of 25, 50 and 75 ppm vitamin C and 1.0 and 3.0 ppm selenium showed a significant increase in the amount of these vitamins (p<0.05). The groups containing 20, 40, 60, 75, 100 and 125 ppm Cd showed a decrease in the amount of reduced glutathione (GSH), stress biomarkers such as malondialdehyde (MDA), oxidized glutathione (GSSG) and 4-hydroxynonenal (4-HNE). The level of GSH increased with increasing concentrations of vitamin C and selenium, while a decrease was observed in the amount of MDA, GSSG and 4-HNE in the medium containing Cd (p <0.05). The superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Red) of the groups containing 60, 75 and 100 ppm Cd were seen to significantly increase compared to the controls. A decrease in the activity of these enzymes was observed with the addition of vitamin C (25, 50 and 75 ppm) to the culture medium in a concentration dependent manner (p <0.05). Levels of amino acids in C. freundii were also determined and the amino acid with the highest concentration was glutamic acid (38.70 ± 1.50 mg / g dw), while the amino acid with the lowest concentration was tryptophan (1.50 ± 0.08 mg / g dw). The amount of leucine, asparagine, glycine, histidine, arginine, valine, aspartic acid, proline, tyrosine, alanine, cysteine, threonine, isoleucine, phenylalanine and lysine increased with increasing concentrations of cadmium. A decrease in the amount of these amino acids was observed after addition of varying concentration of vitamin C. Also, the amount of glutamic acid, serine, glutamine, methionine and tryptophan decreased with increasing concentrations of cadmium and the amount of these amino acids increased with increasing concentrations of vitamin C. The results showed that the use of vitamin C and selenium may provide a beneficial effect on reducing or reversing the toxic effect of cadmium.