Exploring Heavy Metal Tolerant Bacteria from Coal Combustion Residues of Thermal Power Plant as a Possible Bioremediation Candidate

Abstract

Aims: The present investigation aimed to explore heavy metal tolerant microbes in soil samples towards utilisation for bioremediation. Study Design: Indigenous microbes with heavy metal bio remedial capacity were isolated and assessed for the same. Place and Duration of Study: Fly ash contaminated soil was collected from different sites of Bokaro Thermal Power Plant, India with the hypothesis that a heavy metal contaminated location potentially can have many tolerant microbes in it; as microbes of this location are being pre-exposed to several heavy metals for longer duration, are expected to develop heavy metal tolerance mechanism in them. Methodology: Bacterial isolates from the soil were screened by Minimum inhibitory concentration (MIC) technique and also characterised through morphological, biochemical tests, which were finally identified through 16S rDNA sequence analysis. For bio remedial capacity evaluation, Arsenic was assessed through Silver Diethyl Dithio-carbamate (SDDC) method and Lead through Atomic absorption spectrophotometry (AAS). Results: In the present study, two out of nine isolates were found as tolerant to Lead & Arsenic. MICs for IS-05 were 900 ppm for Lead and 1000 ppm for Arsenic respectively and 925 ppm for Lead, 1000 ppm for Arsenic in case of IS-09. Also, the bio remedial capacity for the heavy metals in case of IS-05 was maximum (93%) for Arsenic but IS-09 showed the maximum (88%) bio-remedial capacity for Lead. The16S rDNA extraction, amplification and further phylogenetic analysis identified IS-05 as Bacillus sp. strain JBT18S (NITR-3) and IS-09 identified as Pseudomonas fluorescens through conventional biochemical and other confirmatory tests. Conclusion: Exploring such, can come up with noble indigenous microbe with appreciable bio remedial capacity which can potentially be utilized for bioremediation as it relies on the fact that the tolerant microbes develop several mechanisms in them and by virtue of which they can transform, detoxify, volatilize or putatively entrap metals in the extracellular polymeric substances and even can accumulate harmful chemicals within the cells.