Ubaid Ullah

Arsenic-resistant Klebsiella oxytoca strain AT-02 was isolated from the ground water of the Multan region of Pakistan. The strain displayed high arsenite and arsenate resistance as minimal inhibitory concentration (MIC) was 600ppm and 10,000ppm respectively. The high tolerance of the isolated strain towards arsenate can be postulated due to significant increase in biofilm in response to arsenate. The bacterial strain exposed to 1/2 and 3/4 MIC showed a significant 10 and 12 folds increase in expression of the arsenite efflux gene arsB. Sequential and structural comparison of the arsB gene showed the presence of conserved arsenic binding residues. Arsenic remediation by AT-02 biomass was 50% after 0.5 hours of incubation and 66% in 2 hours. the increase in remediation efficiency with the increase in incubation time indicates its biosorption potential. the arsenic sensitive strain NK11 showed only 4–5% arsenic remediation. Fourier transform infrared spectroscopy (FTIR) analysis confirmed interaction of arsenate and arsenite with functional groups (aromatic amino acid residues) on the cell surface leading to characteristic peak shifts. Thus, the isolated AT-02 has the potential to remediate both arsenite and arsenate from contaminated environmental sites.

The toxicity of arsenic in drinking water is hazardous for human health. Different strategies are used for arsenic removal from drinking water. Nanoparticles with higher adsorption capacities are useful for arsenic remediation. In the current study, magnesium ferrite nanoparticles were synthesised by three different methods followed by their characterisation XRD, SEM, and EDX. The SEM morphology and the porosity of magnesium ferrite nanoparticles were best in case of auto‐combustion method. These particles had an average particle size of about 20–50 nm with spherical shape. These particles showed efficient remediation of arsenic up to 96% within 0.5 h. However, the co‐precipitation and sol‐gel‐based nanoparticles showed arsenic remediation upto85 and 87% at 0.5‐h time point. Moreover, the minimum inhibitory concentration of nanoparticles against two strains E.coli and Pseudomonas aeruginosa was found to be4.0 mg/L of these nanoparticles. However, the sol‐gel‐based nanoparticles showed efficient anti‐microbial activity against E.coli at 4.0 and 8.0 mg/L against Pseudomonas aeruginosa. The co‐precipitation‐based nanoparticles were least efficient both for arsenic remediation and anti‐microbial purposes. Thus, the synthesised auto‐combustion‐based nanoparticles are multifunctional in nature.

The aim of this study was to isolate arsenic-resistant bacteria and to further exploit it for remediation purposes. In the present study, we have isolated arsenic-resistant strain from ground water of Pakistan AT-01. The strain was cultivated at 37 °C in Luria Bertani broth supplemented with different concentrations of arsenate and arsenite. The minimum inhibitory concentration of arsenic against the bacterial isolate was 7 g/L (7000 mg/L) for arsenate and 1.4 g/L (1400 mg/L) for arsenite salt. The bacterial isolate was also characterized both on molecular and biochemical basis. The isolated strain belonged to the Pseudomonas aeruginosa. The high resistance against arsenic offered by the bacteria was exploited further for bioremediation purposes. The bacterial biomass generated from AT-01 strain was able to efficiently remove arsenic with 98% efficiency. Arsenic contamination of ground water is a widespread worldwide problem. The present study shows the potential of high arsenic-resistant bacteria for efficient arsenic removal.