a recombinant bacterium, E. coli SE5000 strain (containing nixA gene), can also
accumulate Ni
2+ from aqueous solution (Fulkerson et al. 1998).
Further, it has been reported that the Ni resistance was enhanced in the recombinant E. coli when introduced with the serine acetyltransferase gene from Ni
hyperaccumulating plant, Thlaspi goesingense (Freeman et al. 2005). Recently,
Hasin et al. (2010) have characterized a methanotrophic bacterium, Methylococcus
capsulatus, which can successfully bioremediate Cr
6+ in a wide range of concentrations (1.4–1000 mgL
À1 of Cr
6+ ). However, a recombinant Cd-resistant rhizosphere bacterial strain, Pseudomonas putida 06909, could detoxify Cd due to its
ability to produce metal-binding peptide (MBP)-EC20 that has high affinity for Cd
(Lee et al. 2001).
In 1970, the first GEMs called “superbug” were constructed to degrade oil by
the transfer of plasmids which could utilize a number of toxic organic chemicals
like octane, hexane, xylene, toluene, camphor, and naphthalene. Microorganisms
that are well adapted to survive in the soil environment may not be able to survive
in aquatic environment and hence cannot be used successfully. Therefore, aquatic
microbes can be used to develop GEBs for bioremediation of aquatic sources. The
use of such organisms would avoid the supplementation of nutrients to the inoculated environment, thereby reducing the costs incurred and maintenance required
(Kulshreshtha 2013). Scientists have developed Anabaena sp. and Nostoc
ellipsosporum by the insertion of linA (from P. paucimobilis) and fcbABC (from
Arthrobacter globiformis), respectively. The gene linA responsible for the biodegradation of lindane (γ-hexachlorocyclohexane), and fcbABC confers the ability to
biodegrade halobenzoates and can be used to remediate these pollutants from water
sources. GEBs have been developed by hybrid gene clusters which alter their
enzymatic activity and substrate specificities (Kulshreshtha 2013). These gene
clusters encode the enzyme possessing improved transforming capability. E. coli
strain is genetically modified to express a hybrid gene cluster for the degradation of
trichloroethylene (TCE) (Kulshreshtha 2013). GEMs possess chemical sensors that
allow the monitoring of contaminant bioavailability rather than just contaminant
presence (Kumar et al. 2013). Bioluminescence-producing GEMs also help us to
understand the spread of microbes in the polluted area and end point of the
bioremediation (Kulshreshtha 2013).
The genetically engineered Pseudomonas strains were the first microbe developed by Indian-born American scientist Dr. Anand Mohan Chakrabarty, with high
catalytic potential to the subject of intellectual property right [US Patent #425944],
which could degrade a variety of petroleum hydrocarbons such as naphthalene,
camphor, xylene, octane, and salicylate. Following the seminal work of
Chakrabarty and his colleagues on the degradation of petroleum and
chloroaromatic compounds (Harvey et al. 1990; Haugland et al. 1990), the possibilities of using genetic engineering technique in biodegradation of organic pollutants had received a breakthrough with many papers published by the Timmis
Laboratory in the mid- and late 1980s (Ramos et al. 1987; Rojo et al. 1987). Thus,
genetic engineering techniques have been proved to be an efficient molecular
approach for the microbial bioremediation of pollutants.
8
G. Saxena et al.
accumulate Ni
2+ from aqueous solution (Fulkerson et al. 1998).
Further, it has been reported that the Ni resistance was enhanced in the recombinant E. coli when introduced with the serine acetyltransferase gene from Ni
hyperaccumulating plant, Thlaspi goesingense (Freeman et al. 2005). Recently,
Hasin et al. (2010) have characterized a methanotrophic bacterium, Methylococcus
capsulatus, which can successfully bioremediate Cr
6+ in a wide range of concentrations (1.4–1000 mgL
À1 of Cr
6+ ). However, a recombinant Cd-resistant rhizosphere bacterial strain, Pseudomonas putida 06909, could detoxify Cd due to its
ability to produce metal-binding peptide (MBP)-EC20 that has high affinity for Cd
(Lee et al. 2001).
In 1970, the first GEMs called “superbug” were constructed to degrade oil by
the transfer of plasmids which could utilize a number of toxic organic chemicals
like octane, hexane, xylene, toluene, camphor, and naphthalene. Microorganisms
that are well adapted to survive in the soil environment may not be able to survive
in aquatic environment and hence cannot be used successfully. Therefore, aquatic
microbes can be used to develop GEBs for bioremediation of aquatic sources. The
use of such organisms would avoid the supplementation of nutrients to the inoculated environment, thereby reducing the costs incurred and maintenance required
(Kulshreshtha 2013). Scientists have developed Anabaena sp. and Nostoc
ellipsosporum by the insertion of linA (from P. paucimobilis) and fcbABC (from
Arthrobacter globiformis), respectively. The gene linA responsible for the biodegradation of lindane (γ-hexachlorocyclohexane), and fcbABC confers the ability to
biodegrade halobenzoates and can be used to remediate these pollutants from water
sources. GEBs have been developed by hybrid gene clusters which alter their
enzymatic activity and substrate specificities (Kulshreshtha 2013). These gene
clusters encode the enzyme possessing improved transforming capability. E. coli
strain is genetically modified to express a hybrid gene cluster for the degradation of
trichloroethylene (TCE) (Kulshreshtha 2013). GEMs possess chemical sensors that
allow the monitoring of contaminant bioavailability rather than just contaminant
presence (Kumar et al. 2013). Bioluminescence-producing GEMs also help us to
understand the spread of microbes in the polluted area and end point of the
bioremediation (Kulshreshtha 2013).
The genetically engineered Pseudomonas strains were the first microbe developed by Indian-born American scientist Dr. Anand Mohan Chakrabarty, with high
catalytic potential to the subject of intellectual property right [US Patent #425944],
which could degrade a variety of petroleum hydrocarbons such as naphthalene,
camphor, xylene, octane, and salicylate. Following the seminal work of
Chakrabarty and his colleagues on the degradation of petroleum and
chloroaromatic compounds (Harvey et al. 1990; Haugland et al. 1990), the possibilities of using genetic engineering technique in biodegradation of organic pollutants had received a breakthrough with many papers published by the Timmis
Laboratory in the mid- and late 1980s (Ramos et al. 1987; Rojo et al. 1987). Thus,
genetic engineering techniques have been proved to be an efficient molecular
approach for the microbial bioremediation of pollutants.
8
G. Saxena et al.