Characterization of a Multi-Metal Resistant Bacillus cereus Strain TWSL_5 and it’s Bioremediation Potential for Cr, Pb, Zn and Fe

Abstract

An effluent sample collected from a textile dyeing factory was screened to isolate metal resistant endogenous bacteria using standard microbiology techniques. A bacterium with the highest metal resistance was characterized by 16S rRNA gene sequencing and the bacterial genome was screened for any possible metal resistant genes using the Polymerase Chain Reaction (PCR). The bioremoval ability of the isolate was evaluated using a multi-metal contaminated industrial effluent. Metal immobilisation was assayed using Scanning Electron Microscopy and Energy-Dispersive X-ray (SEM-EDX) analysis. An isolate (strain TWSL_5) was characterized as a Bacillus cereus strain. MICs of the strain TWSL_5 were found to be 75 mg/L (copper), 50 mg/L (cadmium) and 1000 mg/L (lead). The MIC for lead is among the highest reported for the species, B. cereus. The strain TWSL_5 showed a higher metal removal activity (p<0.001) for copper (93.13±0.17%) and lead (85±1.4%) in spiked cultures. The bacterium could successfully remove lead (100±0.00%), iron (68.22±0.07%), zinc (88.71±0.62%) and chromium (100±0.00%) from an effluent in 7 days of incubation at pH 6 and an insoluble black solid formed was detected as iron by SEM-EDX. The presence of copA in the genome of TWSL_5 was confirmed by PCR followed by sequence analysis. The presence of a gene involved in heavy metal resistance (copA), metal immobilization ability and the multi-metal removal activity of TWSL_5 in both spiked cultures and in an industrial effluent, indicates its potential to be used in metal bioremediation of industrial wastewater.