Bacterial Strains Isolated from Heavy Metals Contaminated Soil and Wastewater with Potential to Oxidize Arsenite

The objective is to develop low cost wastewater treatment systems for the efficient removal of toxic heavy metal ions including arsenic (As). For this, two bacterial strains, one gram negative and other gram positive dubbed as IT6 and S12, were isolated from arsenic contaminated wastewater and soil samples from Sheikhupura, Pakistan. The bacterial isolates were checked for their ability to resist various metal ions and antibiotics and were identified on the basis of 16S rRNA ribotyping. The strains were also checked for their potential to decontaminate arsenite at lab scale. Both strains were identified as Pseudomonas monteilii (IT6) and Bacillus infantis (S12) with minimum inhibitory concentration of 26.5 and 33 mM arsenite, respectively. Apart from arsenite, both bacterial strains showed fair resistance against other metal ions including chromium, lead, cobalt, selenium, zinc, cadmium, and mercury. Both IT6 and S12 showed high potential of arsenite oxidation of 92% and 96% at 37 °C and pH of 7 with 100 µg/mL arsenite after 96 h of incubation. The strains have also shown strong resistance against commonly used antibiotics including amikacin, imipenem, and ciprofloxacin. These bacterial strains are potential candidates to exterminate toxic metal ions from the wastewater for green chemistry due to presence of multiple metal resistance and efficient arsenite oxidizing potential.