Genetically-mutated bacterial strain for detecting estrogenic compound and method for detecting estrogenic compound using the same

Abstract

The present invention relates to a genetically mutated bacteria strain for detecting an estrogenic compound and a method for detecting an estrogenic compound by using the same. More specifically, the present invention relates to a bacteria strain having an ability to detect an estrogenic compound, transformed by plasmid A comprising base sequences in which a gene for encoding a coactivator interacting with an estrogen receptor ligand binding domain (ER LBD) is conjugated to a gene for encoding λCI protein, and plasmid B in which a gene for encoding an estrogen receptor ligand binding domain (ER LBD) is conjugated to a gene for encoding αNTD protein, and a method for detecting an estrogenic compound by using same. The present invention can provide genetically mutated bacteria for detecting an estrogenic compound and a method for detecting an estrogenic compound by using same since the bacteria are based on estrogen receptor protein originated from the human body, and thus are environmentally friendly, and the detection of the bacteria can be performed in a very short time with low cost and labor by virtue of a relatively simple process.

Claims

1. A bacterial strain having an ability of detecting an estrogenic compound, the strain comprising: plasmid A comprising a nucleotide sequence encoding a coregulatory factor protein conjugated with a nucleotide sequence encoding a λCI protein, wherein said coregulatory factor protein is capable of binding an estrogen receptor ligand-binding domain (ER LBD) when said ER LBD is bound to an estrogenic compound; and plasmid B comprising a nucleotide sequence encoding the ER LBD conjugated with a nucleotide sequence encoding an α subunit N-terminal domain (αNTD) protein, wherein the nucleotide sequence encoding the coregulatory factor protein is a nucleotide sequence corresponding to nucleotides at positions 2350 to 5826 in SEQ ID NO: 1 or 2350 to 3090 in SEQ ID NO: 3; the nucleotide sequence encoding the λCI protein is a nucleotide sequence corresponding to nucleotides at positions 1630 to 2348 in SEQ ID NO: 1 and SEQ ID NO: 3; the nucleotide sequence encoding the ER LBD is a nucleotide sequence corresponding to nucleotides at positions 1112 to 1861 in SEQ ID NO: 2; and the nucleotide sequence encoding the αNTD protein is a nucleotide sequence corresponding to nucleotides at positions 359 to 1110 in SEQ ID NO: 2.

2. The bacterial strain according to claim 1, wherein the bacterial strain is any one strain selected from the group comprising Escherichia coli, Bacillus subtilis, Bacillus licheniformis and lactic acid bacteria.

3. The bacterial strain according to claim 1, wherein the estrogenic compound is selected from the group comprising norethynodrel, 5α-androstane, nonylphenol, dodecylphenol, octylphenol, bisphenol A, bisphenol S, bisphenol F, 2-ethylhexyl-4-hydroxybenzoate, 4,4′-dihyroxybenzophenone, 2,4-dihydroxybenzophenone, dihydroxymethoxychlorolefin, o,p′-DDT, dihydroxymethoxychlor (HPTE), 2′,3′,4′,5′-tetrachloro-4-biphenylol, nordihydroguaiaretic acid, aurin, phenolphthalein, phenol red, and a mixture thereof.

4. A method for detecting an estrogenic compound, comprising: providing the bacterial strain having an ability of detecting an estrogenic compound of claim 1; culturing the bacterial strain to which a specimen containing an estrogenic compound is added; and lysing the culture bacterial strain and analyzing a degree of the expression of a reporter protein.

5. The method according to claim 4, wherein the reporter protein is a β-galactosidase, a fluorescent protein or an antibiotic resistance-imparting protein.

6. The method according to claim 5, wherein the fluorescent protein is a green fluorescent protein (GFP), a yellow fluorescent protein (YFP), a red fluorescent protein (RFP) or a luciferase.

7. The method according to claim 4, wherein the degree of the expression of a reporter protein is analyzed using a UV-VIS spectrophotometer.

8. The method according to claim 4, wherein the degree of the expression of the β-galactosidase is measured by adding O-nitrophenyl-β-D-galactopyranoside (ONPG) as a colorimetric reagent after the lysis, and analyzing the expression degree.

9. The bacterial strain according to claim 1, wherein the plasmid A comprises the nucleic acid nucleotide sequence of SEQ ID NO: 1 or 3 and the plasmid B comprises the nucleotide sequence of SEQ ID NO: 2.

10. The bacterial strain according to claim 1, wherein a polypeptide tag encoded by the nucleotide sequence corresponding to nucleotides at positions 1862 to 1885 in SEQ ID NO: 2 is conjugated to the 3′-end of the nucleotide sequence encoding the ER LBD.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram illustrating the case in which a reporter gene is not expressed in the absence of an estrogenic compound (top) and the case in which a reporter gene is expressed by binding of an estrogenic compound to ER LBD (bottom) in bacteria according to the present invention.

(2) FIG. 2A is a graph illustrating the result of confirming an ability of a strain according to the present invention to detect a representative estrogenic compound such as 17β-estradiol.

(3) FIG. 2B is a graph illustrating the result of confirming an ability of a strain according to the present invention to detect a representative estrogenic compound such as 17β-estradiol.

(4) FIG. 3 is a graph illustrating the result of confirming an ability of a strain according to the present invention to detect estrogenic compounds such as estriol and estrone.

(5) FIG. 4A is a graph illustrating the result of confirming an ability of a strain according to the present invention to detect representative environmental hormones such as bisphenol A and nonylphenol.

(6) FIG. 4B is a graph illustrating the result of confirming an ability of a strain according to the present invention to detect representative environmental hormones such as bisphenol A and nonylphenol.

(7) FIG. 5 is a graph illustrating the result of confirming an ability of a strain according to the present invention to detect environmental hormones present in various articles which are available in daily life.

(8) FIG. 6 is a graph illustrating the result of an experiment for comparing the sensitivities of sensor strains using a TIF2 protein and a RIP140 protein, as coregulatory factors interacting with ER LBD according to the present invention, respectively, with respect to a representative estrogen such as estradiol and a representative environmental hormone substance such as bisphenol A.

(9) FIG. 7 is a graph illustrating the result of an experiment for confirming the sensitivity of a sensor strain using a TIF2 protein as a coregulatory factor interacting with ER LBD according to the present invention with respect to various concentrations of estradiol.

(10) FIG. 8 is a graph illustrating an experiment for confirming the sensitivity of a sensor strain using a TIF2 protein as a coregulatory factor interacting with ER LBD according to the present invention with respect to various concentrations of estrone and estriol.

(11) FIG. 9 is a graph illustrating the result of an experiment for confirming the sensibility of a sensor strain using a TIF2 protein as a coregulatory factor interacting with ER LBD according to the present invention with respect to various concentrations of bisphenol A and nonylphenol.

(12) FIG. 10 is a graph illustrating the result of an experiment for confirming the sensibility of a sensor strain using a TIF2 protein as a coregulatory factor interacting with ER LBD according to the present invention with respect to various concentrations of bisphenol S and bisphenol F.

MODES OF THE INVENTION

(13) Hereinafter, the present invention will be described in further detail. In the present invention, to detect an estrogen hormone and various estrogenic compounds, the principle of expressing a reporter gene by specific binding between a coregulatory factor interacting with ER LBD and an ER LBD protein was utilized. That is, when estrogenic compounds are present in a specimen subject to analysis, a corresponding estrogenic compound binds to the ER LBD, thereby forming the interaction between two proteins, and because of the interaction, the expression of a reporter gene is achieved. In addition, the expressed reporter gene is subjected to a color reaction by a colorimetric reagent, and by quantifying a degree of the color reaction, the concentration of the estrogenic compound in the specimen can be exactly quantified.

(14) Therefore, the present invention provides genetically-modified bacteria for detecting an estrogenic compound, and the bacteria according to the present invention have an ability of detecting an estrogenic compound and are transformed by

(15) plasmid A having a base sequence in which a gene encoding a coregulatory factor interacting with ER LBD is conjugated with a gene encoding a λCI protein, and plasmid B in which a gene encoding ER LBD is conjugated with a gene encoding an αNTD protein.

(16) As described above, conventionally, a yeast-based yeast two-hybrid system has been used to detect protein-protein interactions or protein-DNA interactions, but compared to bacteria, yeast has a very high similarity to humans in terms of a gene sequence. For example, yeast contains a protein similar to a coactivator such as human DP97 or REA. Therefore, such proteins are likely to interfere with sensing of an environmental hormone by binding to an estrogen receptor while the environmental hormone is actually sensed by the yeast two-hybrid system. Furthermore, since there are many possibilities for yeast to have proteins, other than the above-described DP97 or REA, capable of binding to an estrogen receptor, the bacteria-based detection method according to the present invention is more advantageous than the yeast two-hybrid system.

(17) When the estrogen receptor protein binds to ligand compounds such as an estrogen, it may bind with a coregulatory factor protein which assists or suppresses a protein activity. In other words, in the present invention, as the ER LBD binding to an estrogenic compound as a ligand is coupled with a coregulatory protein, the estrogenic compound may be detected by a phenomenon of the expression of a reporter gene.

(18) FIG. 1 is a schematic diagram illustrating the case in which a reporter gene is not expressed in the absence of an estrogenic compound (top) and the case in which a reporter gene is expressed by binding of an estrogenic compound to ER LBD (bottom) in bacteria according to the present invention (examples of the reporter gene include lacZ and GFP genes).

(19) The bacteria according to the present invention are bacteria transformed by two types of plasmids, each type of plasmid encoding a protein set involved in the expression of a reporter gene. First, the plasmid A contains a gene encoding a coregulatory factor interacting with ER LBD (represented as a “coactivator” in FIG. 1) and a gene encoding a λCI protein, and the plasmid B contains genes encoding ER LBD and an αNTD protein.

(20) Referring to FIG. 1, the bacteria according to the present invention regulate the expression of a reporter gene by protein sets produced by the two types of plasmids. That is, the coregulatory factor protein and the λCI protein which are expressed by the plasmid A bind upstream of a reporter gene, and the ER LBD and the αNTD protein which are expressed by the plasmid B bind to an RNA polymerase. At this time, to express the reporter gene, it is necessary to have an interaction between a set of the coregulatory factor protein and the λCI protein and a set of the ER LBD and the αNTD protein. Referring to the top view of FIG. 1, when there is no estrogenic compound acting as a ligand, there is no interaction between a set of the coregulatory factor protein and the λCI protein and a set of ER LBD and the αNTD protein, and therefore, the reporter gene is not expressed. Meanwhile, referring to the bottom view of the FIG. 1, when there is an estrogenic compound as a ligand, the estrogenic compound binds to ER LBD, thereby the interaction between a set of the coregulatory factor protein and the λCI protein and a set of ER LBD and the αNTD protein is formed, resulting in the expression of the reporter gene. Therefore, with the bacteria according to the present invention, only when an estrogenic compound is present in a specimen subjected to analysis, a protein may be produced by the expression of the reporter gene.

(21) According to the present invention, as the coregulatory factor protein, any one of various types of coregulatory factors or coactivator proteins, which can interact with ER LBD, may be used, but the present invention is not limited thereto. For example, as the coregulatory factor protein, any one of the proteins selected from the group comprising a RIP140 protein, a TIF2 protein, a TIF1 protein and a SRC1 protein may be considered.

(22) The gene encoding the coregulatory factor interacting with ER LBD or the gene encoding ER LBD, which is included in the plasmid A or B, may be obtained by transcribing mRNA from human genomic DNA, preparing intron-deleted mRNA through splicing of the mRNA, and amplifying the intron-deleted mRNA by PCR using cDNA synthesized by reverse transcription with respect to the mRNA as a template.

(23) In addition, a FLAG sequence for confirming expression of the coregulatory factor protein and the λCI protein may be additionally conjugated to the 3′-end of the gene encoding a coregulatory factor interacting with ER LBD, and in the same manner as described above, a FLAG sequence for confirming expression of the ER LBD and the αNTD protein may be additionally conjugated to the 3′-end of the gene encoding ER LBD. Because of the conjugation of such a FLAG sequence, only expressed proteins can be identified by western blotting recognizing such proteins as specific antibodies.

(24) Specifically, when an RIP140 protein is used as a coregulatory factor, the plasmid A may have a nucleic acid sequence of SEQ ID NO: 1, and the plasmid B may have a nucleic acid sequence of SEQ ID NO: 2. The sequence set forth in SEQ ID NO: 1 includes a gene encoding a λCI protein, a linker amino acid sequence, a gene encoding an RIP140 protein and a FLAG sequence in the 5′ to 3′ direction, and the sequence set forth in SEQ ID NO: 2 includes a gene encoding an αNTD protein, a linker amino acid sequence, a gene encoding ER LBD and a FLAG sequence in the 5′ to 3′ direction.

(25) In addition, when a TIF2 protein is used as a coregulatory factor, the plasmid A may have a nucleic acid sequence of SEQ ID NO: 3, and the plasmid B may have the nucleic acid sequence of SEQ ID NO: 2. The sequence set forth in SEQ ID NO: 3 includes a gene encoding a λCI protein, a linker amino acid sequence, a gene encoding a TIF2 protein and a FLAG sequence in the 5′ to 3′ direction, and the sequence set forth in SEQ ID NO: 2 includes a gene encoding an αNTD protein, a linker amino acid sequence, a gene encoding ER LBD and a FLAG sequence in the 5′ to 3′ direction.

(26) The following examples will be described with reference to E. coli strains as cells transformed by the plasmids A and B according to the present invention, but the target strain is not limited to E. coli, and other than this, all of genetically-manipulated bacterial strains such as Bacillus subtilis, Bacillus licheniformis, lactic acid bacteria, etc. may be used as target strains.

(27) In addition, the target compounds detected by the bacteria according to the present invention include all types of hormones and analogues which can bind to an estrogen receptor, as well as a human estrogen hormone. In the present invention, compounds, for example, various steroid-based hormones (norethynodrel, 5α-androstane, etc.), alkylphenol compounds (nonylphenol, dodecylphenol, octylphenol, etc.), bisphenol-type compounds (bisphenol A, bisphenol S, bisphenol F, etc.), paraben-based compounds generally used as a preservative (2-ethylhexyl 4-hydroxybenzoate, heptyl 4-hydroxybenzoate, etc.), benzophenone-based compounds used as a fixative for a cosmetic fragrance (4,4′-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, etc.), organic chlorine-based substances contained in a pesticide (dihydroxymethoxychlorolefin, o,p′-DDT, dihydroxymethoxychlor (HPTE), 2′,3′,4′,5′-tetrachloro-4-biphenylol, etc.), nordihydroguaiaretic acid also added to food as an antioxidant, aurin widely used as an acid-base indicator, compounds including phenolphthalein, phenol red, etc. may be detected, but the present invention is not limited thereto.

(28) Furthermore, the present invention provides a method for detecting an estrogenic compound using the bacterial according to the present invention, the method including:

(29) preparing bacterial strains according to the present invention;

(30) culturing the bacterial strains by adding a specimen containing an estrogenic compound thereto; and

(31) lysing the culture bacterial strain and analyzing a degree of the expression of a reporter protein.

(32) In other words, in the method according to the present invention, an estrogenic compound in a specimen may be analyzed by utilizing a characteristic of producing a specific protein by the bacteria according to the present invention only when the estrogenic compound, as a ligand, is present in the specimen and binds to ER LBD.

(33) Therefore, in the method according to the present invention, first, the above-described bacterial strain transformed by the plasmids A and B is prepared and cultured with a specimen subjected to analysis, and after the cultured bacterial strain is lysed, a reporter protein expressed by the bacteria is analyzed. At this time, a reporter protein may be produced from a reporter gene only when an estrogenic compound is present in a specimen, and the produced reporter protein may be quantitatively analyzed, thereby detecting the estrogenic compound in the specimen.

(34) In the present invention, a method for analyzing such a reporter protein may vary according to the type of expressed reporter protein, and for example, the reporter protein may be a β-galactosidase, a fluorescent protein or an antibiotic resistance-imparting protein, wherein the fluorescent protein may be a green fluorescent protein (GFP), a yellow fluorescent protein (YFP), a red fluorescent protein (RFP) or a luciferase. The colorimetric or fluorescent protein may be quantitatively analyzed using an instrument such as a UV-VIS spectrophotometer.

(35) In addition, when a β-galactosidase is used as a reporter protein, the analysis may be performed by adding O-nitrophenyl-β-D-galactopyranoside (ONPG) as a colorimetric reagent after the lysis, and analyzing a degree of expression of the reporter protein. For example, when O-nitrophenyl-β-D-galactopyranoside (ONPG) is added as a colorimetric reagent, the added ONPG is degraded by a β-galactosidase, and orthonitrophenol exhibiting strong yellow emission is produced as a degradation product. At this time, a degree of yellow emission may vary according to the concentration of an estrogenic compound present in the specimen, and as the degree of the light emission caused by ONPG may be measured using an UV-VIS spectrophotometer, the concentration of an estrogenic compound present in the specimen can be quantitatively analyzed.

(36) Hereinafter, the present invention will be described in further detail with reference to examples, and the following examples are merely provided to help in understanding the present invention, but the scope of the present invention is not limited thereto.

EXAMPLES

Example 1. Case of Using RIP140 Protein as Coregulatory Factor

Example 1-1. Construction of Plasmids

(37) Full-length RIP140 was amplified by PCR using genomic DNA of a human breast cancer cell line MCF-7 as a template. In the amplification, a FLAG sequence was tagged to confirm protein expression using a specific antibody. hERα LBD (N.sub.304-T.sub.553: amino acid 304, asparagine, through amino acid 553, threonine) was amplified by PCR using DNA complementary to a human breast cancer cell line MCF-7 as a template, and as described above, in the amplification, a FLAG sequence was tagged. Specific conditions for PCR amplification are as follows.

(38) A hERα LBD-FLAG gene was subjected to 30 repeated cycles of a reaction using an Ex-Taq DNA polymerase, sequentially under conditions of 95° C. for 1 minute, 95° C. for 30 seconds, 50° C. for 30 seconds, and 72° C. for 30 seconds. Afterward, finally, the reaction was performed at 72° C. for 5 minutes. For a RIP140-FLAG gene, a reaction was performed using the Ex-Taq DNA polymerase used in the above-described reaction. The reaction was repeated 30 cycles sequentially under conditions of 95° C. for 1 minute, 95° C. for 30 seconds, 50° C. for 30 seconds, and 72° C. for 2.5 minutes. Afterward, finally, the reaction was performed at 72° C. for 5 minutes.

(39) The amplified RIP140-FLAG gene was cleaved with restriction enzymes such as Not I and Bgl II. Subsequently, the cleaved product was inserted into a pACλCI vector cleaved with Not I and BamH I using a ligase, thereby cloning a pACλCI:RIP140-FLAG plasmid (since, due to a BamH I site present in the middle of a RIP140 gene, a recognition sequence was different from that of BamH I, a different restriction enzyme Bgl II, which can bind to a part cleaved with BamH I was used). The amplified hERα LBD-FLAG sequence was also cleaved with Not I and BamH I, and inserted into pBRαNTD cleaved with Not I and BamH I using a ligase, thereby cloning a pBRαNTD::hERα LBD-FLAG sequence.

Example 1-2. Transformation of E. coli

(40) First, competent cells of an E. coli strain, that is, E. coli FW102 OL2-62 (addgene) containing an F′ plasmid in which a λCI operator is present at the lacZ reporter-62 position were constructed. Cells grown from OD.sub.600 (optical density at 600 nm) to OD.sub.0.4 were harvested. Afterward, the cells were treated with 100 mM CaCl.sub.2 for approximately 4 hours, the treated cells were harvested, and then used after the cells were resuspended with 100 mM CaCl.sub.2 at a volume corresponding to 1/50 of the medium volume used in the initial culture.

(41) 1 μL (approximately 100 ng) of each type of plasmid such as pACλCI::RIP140-FLAG and pBRαNTD::hERα LBD-FLAG (plasmids transferred to E. coli DH5α (cloning host) after cloning, amplified and then isolated again) was added to 50 μL of the prepared competent cells, and then stored at 0° C. for approximately 30 minutes. Afterward, after the cells were heated at 42° C. for 1 minute and 40 seconds, the cells were immediately stored at 0° C. for 5 minutes. Subsequently, 1 mL of an LB medium was added to the cells, the cells were cultured at 37° C. for 1 hour and then plated in a medium containing a selective marker such as kanamycin (F′ plasmid selective), ampicillin (pBRαNTD::hERα LBD-FLAG selective), or chloramphenicol (pACλCI::RIP140-FLAG selective).

Example 1-3. Analysis of β-Galactosidase

(42) The E. coli FW102 OL2-62 pACλCI::RIP140-FLAG pBRαNTD::hERα LBD-FLAG strain was inoculated, and cultured up to OD.sub.600˜ 0.4 (20 μM IPTG added; the inducible substance for inducing expression of λCI-RIP140-FLAG and αNTD-hERα LBD-FLAG). Afterward, estrogens and EDCs were added at corresponding concentrations, and the cells were further incubated for 30 minutes. Subsequently, 800 μL of the cells were harvested, and resuspended in 800 μL of a buffer solution (60 mM of Na.sub.2HPO.sub.4, 40 mM of NaH.sub.2PO.sub.4, 10 mM of KCl, 1 mM of MgSO.sub.47H.sub.2O, 400 μM of dithiothreitol), followed by measuring OD.sub.600 (cell content). Afterward, the cells were lysed by ultrasonication and treated with 160 μL of 4 mg/mL ONPG, and thus a time to change a color of the specimen into yellow was recorded. When the color of the specimen changed to yellow, the reaction was stopped with 400 μL of 1M Na.sub.2CO.sub.3. Subsequently, OD.sub.550 (cell debris) and OD.sub.420 (intensity of yellow emission) were measured, and the activity was calculated according to the Miller Unit Formula (1000*(((OD.sub.420−(1.75*OD.sub.550))/(t*v*OD.sub.600)).

(43) FIGS. 2A and 2B show the results of confirming the ability of strains for detecting a representative estrogenic compound, 17β-estradiol. Since an estrogen receptor ligand-binding domain and a RIP140 protein are expressed by isopropyl 1-thio-β-D-galactoside (IPTG), it can be assumed that activity shown when IPTG was not added (−IPTG) is caused by an internal protein resulting from a strain itself. Therefore, as the activity shown when IPTG was not added (−IPTG) was subtracted from that shown when IPTG was added (+IPTG), only activity shown by a protein introduced though gene manipulation may be measured. Referring to FIGS. 2A and 2B, it can be confirmed that the higher the concentration of 17β-estradiol in a specimen, the higher the Miller units. Therefore, it can be seen that the E. coli according to the present invention is effectively used in measurement of the content of 17β-estradiol in a specimen.

(44) In addition, FIG. 3 shows the result of confirming the ability of a strain according to the present invention for detecting different estrogenic compounds such as estriol and estrone, and referring to FIG. 3, like the results shown in FIGS. 2A and 2B, it can be seen that the Miller units increase in proportion to the concentration of an estrogenic compound in a specimen.

(45) Furthermore, FIGS. 4A and 4B show the results of confirming the ability of strains according to the present invention for detecting representative environmental hormones such as bisphenol A and nonylphenol. Referring to FIG. 4, like the above-described results, it can be seen that the higher the concentration of an environmental hormone in a specimen, the higher the Miller units.

(46) Finally, FIG. 5 shows the result of confirming the ability of a strain according to the present invention for detecting environmental hormones present in various articles which are available in daily life. A piece of each article with a size of 0.5 cm×0.5 cm (width×length) was immersed for 30 minutes during the culture of the strain and then removed, and undiluted shampoo was injected at 1/100 of the total volume of the cell culture. Referring to FIG. 5, it can be seen that the strain according to the present invention is able to be used in successfully detecting environmental hormones from various articles.

Example 2. Case of Using TIF2 Protein as Coregulatory Factor

Example 2-1. Construction of Plasmids

(47) The binding domain of TIF2 (TIF2 BD (Q.sub.624-T.sub.869: amino acid 624, glutamine, through amino acid 869, threonine)) was amplified by Polymerase Chain Reaction (PCR) using DNA complementary to human breast cancer cells (MCF-7). During the amplification, a FLAG sequence was tagged to detect protein expression with a specific antibody. hERα LBD (N.sub.304-T553: amino acid 304, asparagine, through amino acid 553, threonine) was amplified by PCR using DNA complementary to human breast cancer cells (MCF-7) as a template. As described above, during the amplification, a FLAG sequence was tagged.

(48) The amplified TIF2 BD-FLAG gene was cleaved with restriction enzymes Not I and BamH I. Afterward, the cleaved product was ligated into a pACλCI vector cleaved with Not I and BamH I using a ligase, thereby cloning a pACλCI::TIF2 BD-FLAG plasmid. The amplified hERα LBD-FLAG was cleaved with Not I and BamH I. As described above, the cleaved product was ligated into pBRαNTD cleaved with Not I and BamH I using a ligase, thereby cloning a pBRαNTD::hERα LBD-FLAG plasmid.

Example 2-2. Transformation of E. coli

(49) First, competent cells of an E. coli strain, that is, E. coli FW102 OL2-62 (addgene) containing an F′ plasmid in which a λCI operator is present at the lacZ reporter-62 position were constructed. Cells grown from OD.sub.600 (optical density at 600 nm) to OD.sub.0.4 were harvested. Afterward, the cells were treated with 100 mM CaCl.sub.2 for approximately 4 hours, the treated cells were harvested, and then used after the cells were resuspended with 100 mM CaCl.sub.2 at a volume corresponding to 1/50 of the medium volume used in the initial culture.

(50) 1 μL (approximately 100 ng) of each type of plasmid such as pACλCI::RIP140-FLAG and pBRαNTD::hERα LBD-FLAG (plasmids transferred to E. coli DH5α (cloning host) after cloning, amplified and then isolated again) was added to 50 μL of the prepared competent cells, and then stored at 0° C. for approximately 30 minutes. Afterward, after the cells were heated at 42° C. for 1 minute and 40 seconds, the cells were immediately stored at 0° C. for 5 minutes. Subsequently, 1 mL of an LB medium was added to the cells, the cells were cultured at 37° C. for 1 hour and then plated in a medium containing a selective marker such as kanamycin (F′ plasmid selective), ampicillin (pBRαNTD::hERα LBD-FLAG selective), or chloramphenicol (pACλCI::RIP140-FLAG selective).

Example 2-3. Analysis of β-Galactosidase

(51) The E. coli FW102 OL2-62 pACλCI::TIF2 BD-FLAG pBRαNTD::hERα LBD-FLAG strain was inoculated, and cultured up to OD.sub.600˜ 0.4 (20 μM IPTG added; the inducible substance for inducing expression of λCI-TIF2 BD-FLAG and αNTD-hERα LBD-FLAG). Afterward, estrogens and EDCs were added at corresponding concentrations, and the cells were further incubated for 30 minutes. Subsequently, 800 μL of the cells were harvested, and resuspended in 800 μL of a buffer solution (60 mM of Na.sub.2HPO.sub.4, 40 mM of NaH.sub.2PO.sub.4, 10 mM of KCl, 1 mM of MgSO.sub.47H.sub.2O, 400 μM of dithiothreitol), followed by measuring OD.sub.600 (cell content). Afterward, the cells were lysed by ultrasonication and treated with 160 μL of 4 mg/mL ONPG, and thus a time to change a color of the specimen into yellow was recorded. When the color of the specimen changed to yellow, the reaction was stopped with 400 μL of 1M Na.sub.2CO.sub.3. Subsequently, OD.sub.550 (cell debris) and OD.sub.420 (intensity of yellow emission) were measured, and the activity was calculated according to the Miller Unit Formula (1000*(((OD.sub.420−(1.75*OD.sub.550))/(t*v*OD.sub.600)).

(52) FIG. 6 shows the result of an experiment for comparing the sensitivities of LE7197 (sensor strain using TIF2: E. coli FW102 OL2-62 pBRαNTD::hERα LBD-FLAG pACλCI::TIF2 BD-FLAG) and LE7182 (sensor strain using RIP140: E. coli FW102 OL2-62 pBRαNTD::hERα LBD-FLAG pACλCI::RIP140-FLAG) according to the present invention with respect to a representative estrogen such as estradiol and a representative environmental hormone substance such as bisphenol A. The corresponding strains were cultured up to the exponential growth phase, and then treated with estradiol and bisphenol A at specific concentrations. Afterward, through β-galactosidase analysis, the expression of a reporter gene, the lacZ gene, was expressed in terms of Miller units. It was confirmed that LE7197 can sense 1 nM of estradiol and 1 μM of bisphenol A, and when treated with 10 nM of estradiol and 10 μM of bisphenol A, a signal-to-noise ratio increases 1.5 to 2 times higher than that of LE7182.

(53) FIG. 7 shows the result of an experimental for confirming the estradiol detecting ability of a sensor strain (LE7197) into which a TIF2 protein is introduced as a coregulatory factor interacting with ER LBD according to the present invention. IPTG serves to express a fusion protein of RNA polymerase αNTD-estrogen receptor protein ligand-binding domain and a fusion protein of λCI-TIF2 binding site proteins in a strain. When IPTG is not treated, the expression of the lacZ gene does not occur even with the treatment of an estrogen. When a slightly higher concentration of estrogen is treated, low sensitivity occurs due to leaky expression of the protein. In the presence of IPTG, the higher the concentration of an estrogen, the higher the intensity of a signal, which indicates that even 1 nM of an estrogen can be detected.

(54) FIG. 8 shows the result of an experiment for confirming sensitivity of a sensor strain (LE7197) using a TIF2 protein as a coregulatory factor interacting with ER LBD according to the present invention with respect to various concentrations of estrone and estriol. It was confirmed that approximately several nM of an estrogen can be detected.

(55) FIG. 9 shows the result of an experiment for confirming the sensibility of a sensor strain (LE7197) using a TIF2 protein as a coregulatory factor interacting with ER LBD according to the present invention with respect to various concentrations of bisphenol A and nonylphenol. It was confirmed that approximately 1 μM of bisphenol A and approximately 100 nM of nonylphenol can be detected.

(56) FIG. 10 shows the result of an experiment for confirming the sensibility of a sensor strain (LE7197) using a TIF2 protein as a coregulatory factor interacting with ER LBD according to the present invention with respect to various concentrations of bisphenol S and bisphenol F. It can be confirmed that the strains according to the present invention can sense several hundred nM of bisphenol S and bisphenol F, which have been widely used as alternatives for bisphenol A in recent years.

(57) In conclusion, the bacterial strain having a detecting ability of an estrogenic compound and the method for detecting an estrogenic compound using the same according to the present invention can detect estrogenic compounds from various specimens in a very short time by a relatively simple process.

INDUSTRIAL APPLICABILITY

(58) The present invention can detect an estrogenic compound using a genetically-modified bacterial strain, and since the present invention is based on a human-derived estrogen receptor protein, the detection can be performed in a very short time with a low cost and a low amount of labor according to an eco-friendly, relatively simple process, and thus can be applied in food, medical and environmental industries, requiring detection of an estrogenic compound.