Metal biosorption by magnetotactic bacteria isolated from fresh water sediments and characterization of extracted magnetosomes

The focus of the present study is to isolate and identify magnetotactic bacteria from fresh water sediments in Salem region, Tamil Nadu. Fresh water sediments were collected and characterized by X-ray diffraction to detect the crystalline nature of particles. Totally 12 isolates were screened for the metal biosorption efficiency in modified nutrient agar plates with 10 mg (lower concentration) of four different metals viz., manganese chloride, zinc sulphate, copper sulphate and potassium dichromate. Followed by testing their ability to tolerate higher concentration of metals viz., 20 mg, 30 mg, 50 mg, 70 mg, 90 mg and 150 mg/50 ml was analyzed. Only four bacteria survived the highest concentration of manganese and zinc (3000 mu g/ml), CuSO4 and K2Cr2O7 at a concentration of 1400 mu g/ml and 1800 mu g/ml, respectively. The four bacterial strains Stenotrophomonas maltophilia, two Pseudomonas aeruginosa strains and Achromobacter xylosoxidans were grown in modified nutrient broth (NB) and Luria Bertani (LB) incorporated with metals such as manganese, zinc, copper and chromium and tested for their efficacy to sustain metal stress. Since the two bacterial strains (SBY and KY1) were able to grow in both medium with a potential to with stand higher metal concentration these strains were further studied. A metal tolerant magnetotactic bacterial strain Pseudomonas aeruginosa SBY was confirmed by TEM analysis to detect the accumulated metal within the cell. As bacterial strains were capable of tolerating higher concentration of metal, they may have a vital role in environmental bioremediation.

Automated summary

This study isolated and identified magnetotactic bacteria with metal tolerance from fresh water sediments in Salem region of Tamil Nadu. Among the strains tested, Pseudomonas aeruginosa and Achromobacter xylosoxidans showed the highest metal tolerance and may play a significant role in environmental bioremediation.