Mycorrhiza enhance the growth of plant by improving nutrition, resistance, and
tolerance against various stresses (Clark and Zeto 2000; Turnau and Haselwandter
2002). They can also be used as bioprotectants, biodegraders, and biofertilizers
(Xavier and Boyetchko 2002). Several studies also report their phytoremediation
potential for heavy metal-polluted soil (Chaudhry et al. 1998; Khan et al. 2000; Khan
2001; Jamal et al. 2002; Hayes et al. 2003; Khan and Ahmad 2006).
5 Genetically Engineered Microorganisms
in Environmental Remediation
Genetic engineering technique which is also called as recombinant DNA technology
is based on the natural genetic interchange in between microorganisms, and the
organism formed is called genetically engineered microorganism (GEM) or modified
microorganism (GMM). These engineered microorganisms have the capacity to
bioremediate the soil, activated sludge, and groundwater by degrading varied chemical. Several researchers also suggest that the genetically modified organisms may
have more potential to remediate the environment than wild ones.
Several gene complexes or plasmids are responsible for degradation of various
environmental pollutants and generally for every compound, and one separate
plasmid is required. According to Ramos et al. (1994), for better understanding,
four categories are described:
1. OCT plasmid for degradation of hexane, decane, and octane.
2. Camphor is decomposed by CAM plasmid.
3. XYL plasmid can degrade xylene and toluenes.
4. NAH plasmid for naphthalene degradation.
The best GMM, for example, Pseudomonas putida, contains the NAH and XYL
plasmid and a hybrid of CAM and OCT plasmid which can degrade camphor,
salicylate, octane, and naphthalene. It can metabolize hydrocarbons more effectively
and grow quickly on crude oil (Markandey and Rajvaidya 2004). This organism
formed by the technology of genetic engineering is known as superbug (oil-eating
bug).
According to Huang et al. (2004), there may be three recommended criteria for
gene recombination and selection as a suitable strain: (1) after cloning, stability and
expression of target gene should be confirmed for selected strains; (2) the strain
should be contaminant tolerant or insensitive; and (3) strains should survive in plant
rhizosphere.
Many rhizobacteria have only limited capability in degrading organic pollutants.
With the use of advance molecular biology, rhizoremediation may get achieved by
the construction of genetically engineered rhizobacteria with the contaminantdegrading gene (Glick 2010).
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A. Mishra et al.
tolerance against various stresses (Clark and Zeto 2000; Turnau and Haselwandter
2002). They can also be used as bioprotectants, biodegraders, and biofertilizers
(Xavier and Boyetchko 2002). Several studies also report their phytoremediation
potential for heavy metal-polluted soil (Chaudhry et al. 1998; Khan et al. 2000; Khan
2001; Jamal et al. 2002; Hayes et al. 2003; Khan and Ahmad 2006).
5 Genetically Engineered Microorganisms
in Environmental Remediation
Genetic engineering technique which is also called as recombinant DNA technology
is based on the natural genetic interchange in between microorganisms, and the
organism formed is called genetically engineered microorganism (GEM) or modified
microorganism (GMM). These engineered microorganisms have the capacity to
bioremediate the soil, activated sludge, and groundwater by degrading varied chemical. Several researchers also suggest that the genetically modified organisms may
have more potential to remediate the environment than wild ones.
Several gene complexes or plasmids are responsible for degradation of various
environmental pollutants and generally for every compound, and one separate
plasmid is required. According to Ramos et al. (1994), for better understanding,
four categories are described:
1. OCT plasmid for degradation of hexane, decane, and octane.
2. Camphor is decomposed by CAM plasmid.
3. XYL plasmid can degrade xylene and toluenes.
4. NAH plasmid for naphthalene degradation.
The best GMM, for example, Pseudomonas putida, contains the NAH and XYL
plasmid and a hybrid of CAM and OCT plasmid which can degrade camphor,
salicylate, octane, and naphthalene. It can metabolize hydrocarbons more effectively
and grow quickly on crude oil (Markandey and Rajvaidya 2004). This organism
formed by the technology of genetic engineering is known as superbug (oil-eating
bug).
According to Huang et al. (2004), there may be three recommended criteria for
gene recombination and selection as a suitable strain: (1) after cloning, stability and
expression of target gene should be confirmed for selected strains; (2) the strain
should be contaminant tolerant or insensitive; and (3) strains should survive in plant
rhizosphere.
Many rhizobacteria have only limited capability in degrading organic pollutants.
With the use of advance molecular biology, rhizoremediation may get achieved by
the construction of genetically engineered rhizobacteria with the contaminantdegrading gene (Glick 2010).
430
A. Mishra et al.