Abstract:
Tellurite reducing bacterial strain was isolated from Zuari estuary, Goa India which could tolerate 5.5?mM potassium tellurite with a minimum inhibitory concentration of 6?mM. This strain was designated as GUSDZ9 and was identified as Shewanella baltica (accession number: MF350629) based on 16S rRNA gene sequencing and BLAST analysis. The Diethyl-dithiocarbamate based colorimetric analysis clearly demonstrated a complete reduction of 2?mM tellurite to elemental tellurium during the late stationary phase. Te Nanoparticles (TeNPs) biosynthesis which initiated at early log phase (i.e. 4?h) was evidently monitored through colour change and a peak due to surface plasmon resonance at 210?nm using UV-Vis spectroscopic analysis. X-ray crystallographic studies and transmission electron microscopy revealed unique nano-rods with a diameter ranging from 8 to 75?nm. Energy dispersive X-ray analysis further confirmed the presence of pure tellurium. The biogenic TeNPs at 10 and 5?mu g/mL evidently demonstrated 90% degradation of methylene blue dye and anti-biofilm activity against potential Gram-positive and Gram-negative human pathogens respectively. The alkaline comet assay revealed time and dose-dependent genotoxicity at concentrations higher than 15?mu g/mL of TeNPs. This study clearly demonstrated the potential of Shewanella baltica strain GUSDZ9 in bioremediation of toxic tellurite through bio-reduction into elemental tellurium and involvement of biogenic TeNPs in the photo-catalytic reduction of methylene blue and anti-biofilm activity. This is the first report of its kind on the synthesis of biogenic TeNPs from Shewanella baltica demonstrating photo-catalytic, anti-biofilm activity as well as genotoxicity.
