and opdA (Somara et al. 2002). During microbial degradation of atrazine, the
degrading microbe Citrichoccus spp. strain TT3 possessed the genes trzN, atzB,
and atzC, all of which were involved in the biodegradation process of atrazine (Yang
et al. 2018).
Similarly, genes responsible for the degradation of chlorobenzene acids, other
halogenated pesticides and toxic wastes have been identified. Friello et al. (2001)
successfully produced Pseudomonas, a multiplasmid containing oxidizers of aliphatic, aromatic, terpenic, and polyromatic hydrocarbons. Pseudomonas putida that
contained XYL and NAH plasmid, as well as hybrid plasmid derived by the
recombinating components of CAM and OCT developed by conjugation could
degrade camphor, octane, salicylate, and naphthalene (Sayler and Ripp 2000).
Degradation of environmental pollutants by genetically engineered microorganisms
is primarily focused on genetically engineered bacteria using various genetically
engineered technologies, such as modification and substrate specificity by
Comamonas testosteroni strain VP44 (Hrywna et al. 1999). For the degradation of
polychlorinated biphenyls, chromosomally located PCB catabolic genes of
R. eutropha A5, Acromobacter spp. LBS1C1, and A. denitrificans JB1 were transferred into the heavy metal–resistant strain R. eutropha CH34 by natural conjugation
(Menn et al. 2008).
For heavy metals, Sriprang et al. (2003) introduced Arabidopsis thaliana gene for
phytochelatin synthase (PCS; PCSATt) into the Mesorhizobium huakuii subspp.
rengei strain B3, which established a symbiosis between the M. huakuii subs. rengei
strain B3 and Astragalus sinicus. The gene was expressed to produce phytochelatins,
and it accumulated CD
2+ , under the control of the bacteroid-specific promoter of the
nifH gene (encoding Fe protein, dinitrogenase reductase) (Sussman et al. 1988).
Finally, the use of genetically engineered microorganism (GEM) strains as an
inoculum during seeding avoids problems related with competition between strains
in mixed culture. However, there is much controversy about the release of such
genetically engineered microbial strains into the environment, so field testing of
these organisms must be delayed until safety and environmental damage issues are
resolved (Wackett 2004).
2.9.1 Adaption and Development of New Degradation
Capabilities
Microorganisms can occupy an infinite variety of niches in the environment because
of their rapid growth rate, large numbers, and small size. The breadth of selective
pressures experienced by these microbes provided them the opportunity to develop
tremendous biochemical diversity. There is an important selective advantage in the
ability to utilize a new substrate in otherwise carbon-limited soils. A number of
microorganisms possess the enzymes required to degrade xenobiotic molecules,
whose structures are apparently foreign to anything previously seen in nature. The
2 Bioremediation of Pesticides: An Eco-Friendly Approach for Environment. . .
55
degrading microbe Citrichoccus spp. strain TT3 possessed the genes trzN, atzB,
and atzC, all of which were involved in the biodegradation process of atrazine (Yang
et al. 2018).
Similarly, genes responsible for the degradation of chlorobenzene acids, other
halogenated pesticides and toxic wastes have been identified. Friello et al. (2001)
successfully produced Pseudomonas, a multiplasmid containing oxidizers of aliphatic, aromatic, terpenic, and polyromatic hydrocarbons. Pseudomonas putida that
contained XYL and NAH plasmid, as well as hybrid plasmid derived by the
recombinating components of CAM and OCT developed by conjugation could
degrade camphor, octane, salicylate, and naphthalene (Sayler and Ripp 2000).
Degradation of environmental pollutants by genetically engineered microorganisms
is primarily focused on genetically engineered bacteria using various genetically
engineered technologies, such as modification and substrate specificity by
Comamonas testosteroni strain VP44 (Hrywna et al. 1999). For the degradation of
polychlorinated biphenyls, chromosomally located PCB catabolic genes of
R. eutropha A5, Acromobacter spp. LBS1C1, and A. denitrificans JB1 were transferred into the heavy metal–resistant strain R. eutropha CH34 by natural conjugation
(Menn et al. 2008).
For heavy metals, Sriprang et al. (2003) introduced Arabidopsis thaliana gene for
phytochelatin synthase (PCS; PCSATt) into the Mesorhizobium huakuii subspp.
rengei strain B3, which established a symbiosis between the M. huakuii subs. rengei
strain B3 and Astragalus sinicus. The gene was expressed to produce phytochelatins,
and it accumulated CD
2+ , under the control of the bacteroid-specific promoter of the
nifH gene (encoding Fe protein, dinitrogenase reductase) (Sussman et al. 1988).
Finally, the use of genetically engineered microorganism (GEM) strains as an
inoculum during seeding avoids problems related with competition between strains
in mixed culture. However, there is much controversy about the release of such
genetically engineered microbial strains into the environment, so field testing of
these organisms must be delayed until safety and environmental damage issues are
resolved (Wackett 2004).
2.9.1 Adaption and Development of New Degradation
Capabilities
Microorganisms can occupy an infinite variety of niches in the environment because
of their rapid growth rate, large numbers, and small size. The breadth of selective
pressures experienced by these microbes provided them the opportunity to develop
tremendous biochemical diversity. There is an important selective advantage in the
ability to utilize a new substrate in otherwise carbon-limited soils. A number of
microorganisms possess the enzymes required to degrade xenobiotic molecules,
whose structures are apparently foreign to anything previously seen in nature. The
2 Bioremediation of Pesticides: An Eco-Friendly Approach for Environment. . .
55