Molecular approaches to bioremediation
Bioremediation can be defined as a process that uses microorganisms, fungi, green plants or their enzymes to return the natural environment altered by contaminants to its original condition. A major advantage of bioremediation is its reduced cost compared to conventional cleanup techniques – the cost of remediation for all contaminated sites in the USA alone is estimated to be $1.7 trillion (Molecular approaches in bioremediation. Curr Opin Biotechnol. Nov 12 2008). In addition, bioremediation is often a permanent solution providing complete transformation of the pollutant to its molecular constituents like carbon dioxide and water rather than a partial method that transfers wastes from one phase to another. Unfortunately, there are many man-made compounds that lack good biological catalysts, and many instances where good biocatalysts fail to transform pollutants in the environment.
Bacteria have enormous potential for cleaning up wastes; however, the interactions between bacteria and pollutants are complex and suitable outcomes do not always take place. Hence, molecular approaches are being applied to enhance bioremediation. One advance in bioremediation to improve the stability of the biocatalyst is to create a system where degradation occurs in the area near the roots of plants known as the rhizosphere. In rhizoremediation, the bacteria degrade the pollutants while the plant roots provide a niche for the microorganism and key nutrients. The advantages of rhizoremediation include the ability of plant roots to provide a large surface area for bacterial propagation and biofilm formation, the roots transport the bacteria through the contaminated soil, the roots provide a niche for the bacteria by providing nutrients, and the roots facilitate oxygen exchange. Successful rhizoremediation systems have been established for pollutants such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls (PCBs), fuels, metals, and pesticides such as parathion.
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Directed evolution or DNA shuffling is a powerful mutagenesis technique that mimics the natural molecular evolution of genes in order to efficiently re-design them. Its power lies in the fact that it can introduce multiple mutations into a gene in order to create new enzymatic activity, which can be discovered by a suitable method of selection (bioassays). Family shuffling applies DNA shuffling to groups of related genes to combine them in a manner that accelerates directed evolution. Genome shuffling recombines the chromosomes of several bacteria to enhance the activity of the whole organism.
Metabolic engineering involves redirecting a cell’s metabolism to achieve a particular goal using recombinant engineering. This technique has been used to create bacterial strains that degrade chlorinated ethenes through the addition of several cloned enzymes to the cell. Metabolic engineering has also been used successfully to handle difficult mixtures of pollutants.
Whole-transcriptome profiling using DNA microarrays has the advantage that the relative amount of transcripts from the whole genome may be easily determined compared to such techniques like proteomics. To understand the metabolism of bacteria in the rhizosphere, researchers have begun to utilize whole-genome profiling.
Although a tremendous amount of work remains to be performed, significant advances have been made through protein engineering and through metabolic engineering for the purposes of bioremediation. However, even though whole-transcriptome profiling and proteomics are utilized routinely in some disciplines, they remain to be utilized extensively in bioremediation. Furthermore, it is important to ensure engineered strains for field use are competitive; rhizoremediation can provide a niche for these engineered bacteria. Chromosomal integration of introduced genes can limit horizontal gene transfer to other species, but this should also be empirically verified to ensure that no adverse environmental effects occur.
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Tags: Bacteria, Biofilms, Biology, Biotechnology, Environment, Genetics, Microbiology, Podcast, Science
good study material on your site.i want to study more about it. im PRE. PH.D.STudent of Environmental Engineering atG.J.U.OF SCIENCE &TECHNOLOGY-INDIA