Abstract
Cadmium resistant bacterium, isolated from industrial wastewater, was characterized as Salmonella enterica 43C on the basis of biochemical and 16S rRNA ribotyping. It is first ever reported S. enterica 43C bared extreme resistance against heavy metal consortia in order of Pb2+>Cd2+>As3+>Zn2+>Cr6+>Cu2+>Hg2+. Cd2+ stress altered growth pattern of the bacterium in time dependent manner. It could remove nearly 57 % Cd2+ from the medium over a period of 8 days. Kinetic and thermodynamic studies based on various adsorption isotherm models (Langmuir and Freundlich) depicted the Cd2+ biosorption as spontaneous, feasible and endothermic in nature. Interestingly, the bacterium followed pseudo first order kinetics, making it a good biosorbent for heavy metal ions. The S. enterica 43C Cd2+ processivity was significantly influenced by temperature, pH, initial Cd2+ concentration, biomass dosage and co-metal ions. FTIR analysis of the bacterium revealed the active participation of amide and carbonyl moieties in Cd2+ adsorption confirmed by EDX analysis. Electron micrographs beckoned further surface adsorption and increased bacterial size due to intracellular Cd2+ accumulation. An overwhelming increase in glutathione and other non-protein thiols levels played a significant role in thriving oxidative stress generated by metal cations. Presence of metallothionein clearly depicted the role of such proteins in bacterial metal resistance mechanism. The present study results clearly declare S. enterica 43C a suitable candidate for green chemistry to bioremediate environmental Cd2+.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0225-9) contains supplementary material, which is available to authorized users.
Highlights
Heavy metal pollution has become a major environmental problem worldwide (Ali et al 2013)
Isolation and purification of cadmium resistant bacteria To isolate cadmium resistant bacteria, 100 μL of wastewater sample was spread on Luria-Bertani (LB) agar (1 % NaCl, 1 % tryptone, 0.5 % yeast extract and 1.5 % agar) plates supplemented with 1 mM Cd2+
Screening of Cd2+ resistant bacteria The wastewater samples were spread on LB agar plates supplemented with 1 mM Cd2+
Summary
Heavy metal pollution has become a major environmental problem worldwide (Ali et al 2013). Non-essential and non-biodegradable heavy metal with half-life of 20 years (Martelli et al 2006; Aksoy et al 2014; Xu et al 2014; Vinodini et al 2015). It is soft, silver-white, electropositive metal having atomic number 48, atomic mass 112.41, density 8.64 g/cm and melting. No physiological role of cadmium in human cellular metabolism has been reported so far and it is extremely toxic in. It has been reported to cause osteoporosis and fractures, anemia, eosinophilia, anosmia, apoptosis, diabetes mellitus, oncogenes activation, Itai–Itai disease and chronic pulmonary problems (Waisberg et al 2003; Edwards and Prozialeck 2009; Yazdankhah et al 2010)
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