In vivo studies to elucidate the role of extracellular polymeric substances from Azotobacter in immobilization of heavy metals.
The role of extracellular polymeric substances (EPS) produced by the heavy metal-resistant strain of Azotobacter spp. in restricting the uptake of cadmium (Cd) and chromium (Cr) by wheat plants cultivated in soils contaminated with the respective heavy metals has been demonstrated. A heavy metal-resistant strain of Azotobacter spp. was isolated and identified. Minimum inhibitory concentrations (MIC) of Cd2+ and CrO4(2-) were determined to be 20 and 10 mg L(-1), respectively. Under in vitro conditions, the EPS produced by the strain could bind 15.17 +/- 0.58 mg g(-1) of Cd2+ and 21.9 +/- 0.08 mg g(-1) of CrO4(2-). Fourier transform infrared spectra of the EPS revealed the presence of functional groups like carboxyl (-COOH) and hydroxyl (-OH), primarily involved in metal ion binding. Under pot culture experiments, the isolated strain of Azotobacter was added to the metal-contaminated soils in the form of free cells and immobilized cells. The total Azotobacter count and plant metal concentrations under different treatments showed a negative coefficient between the Azotobacter population and plant Cd (-0.496) and Cr (-0.455). Thus it could be inferred that Azotobacter spp. is involved in metal ion complexation either through EPS or through cell wall lipopolysaccharides (LPS).
Joshi
Prachi M
PM
Environmental Biotechnology Division, National Environmental Engineering Research Institute (NEERI), Nehru Marg, Nagpur-440020, India.
Juwarkar
Asha A
AA
D000327:Adsorption; D001395:Azotobacter / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D002473:Cell Wall / Q000737:chemistry; D002840:Chromates / Q000737:chemistry; D002857:Chromium / Q000032:analysis / Q000737:chemistry; D007477:Ions; D008070:Lipopolysaccharides / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D014908:Triticum / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000302:isolation & purification / Q000633:toxicity
D002840:Chromates; D007477:Ions; D008070:Lipopolysaccharides; D019216:Metals, Heavy; D011108:Polymers; D014874:Water Pollutants, Chemical; D002104:Cadmium; D002857:Chromium