92
Regulatory gene usually emerges from microorganisms that are resistant to a specific pollutant. Using genetic engineering, a promoter sequence from one microbial
species can be fused to a reporter gene from other microbes. The fused protein can
be introduced into bacterial chromosome, and it allows better stability of the system. The regulatory gene is activated by specific environmental condition; the activation would lead to synthesis of proteins, the activity which helps the cell combat
the hazardous material or adapt it. It is important to note that the detection of environmental molecules using microbial biosensor is generally based on assays where
the expression of the reporter gene is either inducible or constitute.
Green fluorescence protein, luciferase, and β-galactosidase are used as a reporter
protein in genetically modified biosensor (Table 4.2). One of the most popularly and
commonly used reporter genes is known as green fluorescence protein. This is due
to easy availability, the lack of requirements for a substrate or the co-factor, and the
ability to use single-cell detection. Figure 4.3 represents the bacterial biosensor for
detection of specific pollutants; specific pollutant is identified by regulatory gene,
which then activates the promoter attached to the reporter gene. The transcription is
initiated in the synthesis of a regulatory protein and produces the measurable signal.
4.5.1 Genetically Modified Bacterial Biosensor for Persistent
Organic Pollutants
As discussed earlier, pollutants are a serious problem in both developed and developing countries. It is necessary to monitor pollutants in the environment. To detect
persistent organic pollutants, genetically engineered microbial biosensors have
been developed by various researchers. Table 4.3 summarizes the different types of
bacterial biosensors for the detection of persistent organic pollutants and
heavy metals.
4.5.2 Genetically Modified Bacterial Biosensor
for Polychlorinated Biphenyls
Polychlorinated biphenyls are synthetic organochlorine compounds, which contain
multiple no. of chlorine atoms with a wide range of industrial applications due to its
chemical and thermal stability. Polychlorinated biphenyls are most widely identified xenobiotic compounds in the environment. Leedjarv et al. (2006) constructed a
biosensor to determine the phenols in leachate site and groundwater. In this study,
phenol’s (methylphenols, dimethylphenol, and resorcinol) availability was assessed
by transcriptional fusion (DmpR-Po-lux CDABE) between regulatory (DmpR) and
reporter gene (lux). The sensor was able to detect phenols with 4 h incubation and
detectable limit reached up to 0.08 mg/L for phenol and 0.03 mg/L for methyl
S. Ganesan and N. Vasudevan
Regulatory gene usually emerges from microorganisms that are resistant to a specific pollutant. Using genetic engineering, a promoter sequence from one microbial
species can be fused to a reporter gene from other microbes. The fused protein can
be introduced into bacterial chromosome, and it allows better stability of the system. The regulatory gene is activated by specific environmental condition; the activation would lead to synthesis of proteins, the activity which helps the cell combat
the hazardous material or adapt it. It is important to note that the detection of environmental molecules using microbial biosensor is generally based on assays where
the expression of the reporter gene is either inducible or constitute.
Green fluorescence protein, luciferase, and β-galactosidase are used as a reporter
protein in genetically modified biosensor (Table 4.2). One of the most popularly and
commonly used reporter genes is known as green fluorescence protein. This is due
to easy availability, the lack of requirements for a substrate or the co-factor, and the
ability to use single-cell detection. Figure 4.3 represents the bacterial biosensor for
detection of specific pollutants; specific pollutant is identified by regulatory gene,
which then activates the promoter attached to the reporter gene. The transcription is
initiated in the synthesis of a regulatory protein and produces the measurable signal.
4.5.1 Genetically Modified Bacterial Biosensor for Persistent
Organic Pollutants
As discussed earlier, pollutants are a serious problem in both developed and developing countries. It is necessary to monitor pollutants in the environment. To detect
persistent organic pollutants, genetically engineered microbial biosensors have
been developed by various researchers. Table 4.3 summarizes the different types of
bacterial biosensors for the detection of persistent organic pollutants and
heavy metals.
4.5.2 Genetically Modified Bacterial Biosensor
for Polychlorinated Biphenyls
Polychlorinated biphenyls are synthetic organochlorine compounds, which contain
multiple no. of chlorine atoms with a wide range of industrial applications due to its
chemical and thermal stability. Polychlorinated biphenyls are most widely identified xenobiotic compounds in the environment. Leedjarv et al. (2006) constructed a
biosensor to determine the phenols in leachate site and groundwater. In this study,
phenol’s (methylphenols, dimethylphenol, and resorcinol) availability was assessed
by transcriptional fusion (DmpR-Po-lux CDABE) between regulatory (DmpR) and
reporter gene (lux). The sensor was able to detect phenols with 4 h incubation and
detectable limit reached up to 0.08 mg/L for phenol and 0.03 mg/L for methyl
S. Ganesan and N. Vasudevan