metal concentration [69, 75]. The metabolism and intrinsic property of some bacteria associated with cell wall structure and the presence of extracellular polymeric substances are able to tolerate metal ions. Some other bacteria resist to metal by using resistance mechanisms such as active transport, efflux pump, intra- and extracellular sequestration, methylation, toxic chemical transfer to less toxic chemical through enzymatic transformation of redox reaction, and sensitivity reduction of cellular targets to metal (Figure 3.5) [76].
The heavy metals are reduced by using immobilization process. The Cr(VI) is reduced to Cr(III) by using both anaerobic and aerobic microorganisms. The presence of oxygen in aerobic condition and the reduction of Cr(VI) by microbes are generally catalyzed though soluble enzyme and lessening of Cr(VI) to Cr(III) by microbes as an eco-friendly method [77]. The bacterial strain such as E. coli, Pseudomonas putida, Desulfovibrio sp., Bacillus sp., Shewanella sp., Arthobacter sp., Microbacterium sp., and Cellulomonas sp., which reduce Cr(VI) isolated from contaminated area [78]. Arsenic compound used as an electron donor or accepter by microorganisms and possess the detoxification of arsenic, with pushes up to the membrane level of cells to eradicate As(III) from cells and metabolites of cell, finally As(V) removal arise [69]. Anaerobic bacteria are capable to reduce contaminated As(V) to As(III) and sulfate to elemental sulfur and precipitates in the form of arsenite sulfide [79]. Therefore sulfide precipitation is a useful mechanism for reduction of arsenic. The EPS of Chryseomonas luteola immobilized the metal ions such as cadmium, cobalt, nickel, and copper through adsorption [64].
Figure 3.5 Schematic diagram of bioimmobilization.
3.6 Conclusion
Biodetoxification is mainly treated by biosorption, bioleaching, biovolatilization, bioimmobilization, and bioaccumulation mechanism of bacterial cell. These processes are economically significant. EPSs present in bacterial cell are involved in bacteria and metal ion interaction and established the process of biosorption. The metals transform toxic to less toxic or less available or removed from environment by using these mechanisms. Among all mechanisms, biosorption mechanism is more effective and beneficial, and it includes ion-exchange and precipitation mechanisms. These detoxification mechanisms are eco-friendly and cost effective.
References
1. Singh, P. and Cameotra, S.S., Enhancement of metal bioremediation by use of microbial surfactants. Biochem. Biophys. Res. Commun., 319, 291, 2004.
2. Luoma, S.N. and Rainbow, P.S., Metal contamination in aquatic environments. Science and lateral management, Cambridge University press, Cambridge, 2008.
3. Tan, F., Wang, M., Wang, W., Lu, Y., Comparative evaluation of the cytotoxicity sensitivity of six fish cell lines to four heavy metals in vitro. Toxicol. In Vitro, 22, 164, 2008.
4. Yadav, S.K., Heavy metals toxicity in plants: an overview on the role of glutathione and phytochelatins in heavy metal stress tolerance of plants. S. Afr. J. Bot., 76, 167, 2010.
5. Paul, D., Pandey, G., Pandey, J., Jain, R.K., Accessing microbial diversity for bioremediation and environmental restoration. TRENDS Biotechnol., 23, 135, 2005.
6. Barkay, T. and Schaefer, J., Metal and radionuclide bioremediation: issues, considerations and potentials. Curr. Opin. Microbiol., 4, 318, 2001.
7. Lloyd, J.R., Microbial reduction of metals and radionuclides. FEMS Microbiol. Rev., 27, 411, 2003.
8. Chien, C.C., Lin, B.C., Wu, C.H., Biofilm formation and heavy metal resistance by an environmental Pseudomonas sp. Biochem. Eng. J., 78, 132, 2013.
9. Ancion, P.Y., Lear, G., Lewis, G.D., Three common metal contaminants of urban runoff (Zn, Cu & Pb) accumulate in freshwater biofilm and modify embedded bacterial communities. Environ. Pollut., 158, 2738, 2010.
10. Beech, I.B. and Cheung, C.S., Interactions of exopolymers produced by sulphate-reducing bacteria with metal ions. Int. Biodeter. Biodegr., 35, 59, 1995.
11. Baker-Austin, C., Wright, M.S., Stepanauskas, R., McArthur, J.V., Co-selection of antibiotic and metal resistance. Trends Microbiol., 14, 176, 2006.
12. Costley, S.C. and Wallis, F.M., Treatment of heavy metal-polluted wastewaters using the biofilms of a multistage rotating biological contactor. World J. Microbiol. Biotechnol., 17, 71, 2001.
13. Nayak, S.K., Nayak, S., Patra, J.K., Rhizobacteria and its biofilm for sustainable agriculture: A concise review, in: New and Future Developments in Microbial Biotechnology and Bioengineering: Microbial Biofilms, M.K. Yadav and B.P. Singh (Eds.), pp. 165–175, Elsevier, Amsterdam, Netherlands, 2020.
14. Lovley, D.R. and Coates, J.D., Bioremediation of metal contamination. Curr. Opin. Biotechnol., 8, 285, 1997.
15. Tchounwou, P.B., Yedjou, C.G., Patlolla, A.K., Sutton, D.J., Heavy metal toxicity and the environment, in: Molecular, clinical and environmental toxicology, A. Luch (Ed.), pp. 133–164, Springer, Basel, 2012.
16. He, Z.L., Yang, X.E., Stoffella, P.J., Trace elements in agroecosystems and impacts on the environment. J. Trace Elem. Med. Bio., 19, 125, 2005.
17. Shallari, S., Schwartz, C., Hasko, A., Morel, J.L., Heavy metals in soils and plants of serpentine and industrial sites of Albania. Sci. Total Environ., 209, 133, 1998.
18. Arruti, A., Fernández-Olmo, I., Irabien, Á., Evaluation of the contribution of local sources to trace metals levels in urban PM2. 5 and PM10 in the Cantabria region (Northern Spain). J. Environ Monit., 12, 1451, 2010.
19. Pacyna, J.M., Monitoring and assessment of metal contaminants in the air, in: Toxicology of Metals, L.W. Chang, L. Magos, T. Suzuli (Eds.), pp. 9–28, CRC Press, Boca Raton, FL, 1996.
20. Rajaganapathy, V., Xavier, F., Sreekumar, D., Mandal, P.K., Heavy metal contamination in soil, water and fodder and their presence in livestock and products: a review. J. Environ. Sci. Technol., 4, 234, 2011.
21. Gautam, R.K., Sharma, S.K., Mahiya, S., Chattopadhyaya, M.C., Contamination of heavy metals in aquatic media: transport, toxicity and technologies for remediation, in: Heavy Metals In Water: Presence, Removal and Safety, S. Sharma (Ed.), pp. 1–24, Royal Society of Chemistry, London, United Kingdom, 2014.
22. Wuana, R.A. and Okieimen, F.E., Heavy metals in contaminated soils: a review of sources, chemistry, risks and best available strategies for remediation. Isrn Ecology, 2011, 402647, 2011.
23. Agency for Toxic Substances and Disease Registry (ATSDR), Toxicological Profile for Arsenic TP-92/09, Georgia: Center for Disease Control, Atlanta, 2000.
24. Tchounwou, P., Development of Public Health Advisories for Arsenic in Drinking Water. Environ. Health Rev., 14, 211, 1999.
25. Centeno, J.A., Tchounwou, P.B., Patlolla, A.K., Mullick, F.G., Murakata, L., Meza, E., Yedjou, C.G., Environmental pathology and health effects of arsenic poisoning, in: Managing Arsenic in the Environment: From Soil to Human Health, R. Naidu, E. Smith, G. Owens, P. Bhattacharya, P. Nadebaum (Eds.), pp. 311–327, CSIRO Publishing, Collingwood, Australia, 2006.
26. Li, J.H. and Rossman, T.G., Inhibition of DNA ligase activity by arsenite: a possible mechanism of its comutagenesis. Mol Toxicol., 2, 1, 1989.
27. Hartmann, A. and Speit, G., Comparative investigations of the genotoxic effects of metals in the single cell gel (SCG) assay and the sister chromatid exchange (SCE) test. Environ. Mol. Mutagen., 23, 299, 1994.
28.