Pharmaceutical products occurring in freshwater bodies create numerous problems for the water bodies owing to their bio-toxic nature. In order to remove such pharmaceutical pollutants, a novel Er-doped Bi4O5Br2/ g-C3N5 nanocomposite was prepared by one-pot synthesis and applied for the photocatalytic removal process. The Er ions doped on the surface of Bi4O5Br2/ g-C3N5 nanocomposite exhibited 97% degradation of tetracycline in 60 min under visible light irradiation, which is higher than pure g-C3N5 and Bi4O5Br2 photocatalysts. The improved photocatalytic properties are attributed to the outstanding visible light harvesting capacity and quick charge carrier separation efficiency which greatly reduced the recombination rate in the heterojunctions. Based on radical trapping experiments, the •O2 −, h+ and •OH radicals played a prominent role in the photodegradation reactions under visible light. Finally, the ternary Er-doped Bi4O5Br2/ g-C3N5 nanocomposite is effectively recyclable with quite a stable photocatalytic removal rate. This work enables a new perspective on the rational design of rare-earth-based nanocomposites for various pharmaceutical pollutants treatment processes.

Single-atom Pd clusters anchored on t-BaTiO3 material was synthesized using hydrothermal and ultrasonic methods for the effective piezoelectric catalytic degradation of pollutants using vibration energy. XRD patterns of BaTiO3 loaded with monoatomic Pd were obtained before and after calcining, and showed typical cubic-phase BTO. TEM and HAADF-STEM images indicated single-atom Pd clusters were successfully introduced into the BaTiO3. The piezoelectric current density of the prepared Pd-BaTiO3 binary composite was significantly higher than that of the pristine BaTiO3. Under mechanical vibration, the nanomaterial exhibited a tetracycline decomposition rate of ~95 % within 7 h, which is much higher than the degradation rate of 56.7 % observed with pure BaTiO3. Many of the piezo-induced electrons escaped to the Pd-doped BaTiO3 interface because of Pd’s excellent conductivity. Single-atom Pd clusters help promote the separation of the piezo-induced electrons, thereby achieving synergistic catalysis. This work demonstrates the feasibility of combining ultrasonic technology with the piezoelectric effect and provides a promising strategy for the development of ultrasonic and piezoelectric materials.

A porous-carbon material UiO-66-C was prepared from metal–organic frameworks UiO-66 by carbonization in inert gas atmosphere. Physicochemical properties of UiO-66-C materials were well characterized by Powder X-ray diffraction (PXRD), Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR), Raman spectrometer, N2 adsorption/ desorption isotherms (BET), and the adsorption properties of the products were studied UiO-66-C has a high specific surface area up to 1974.17 m2/ g. Besides, the adsorption capacity of tetracycline could reach 678.19 mg/g, the adsorption processes agreed well with the pseudo-second-order kinetic model and Langmuir isotherm model.

Bi2MoO6 (BMO) via the structure-directing role of CO(NH2)2 is successfully prepared via a facile solvothermal route. The structure, morphology, and photocatalytic performance of the nanoflake BMO are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fluorescence spectrum analysis (PL), UV-vis spectroscopy (UVvis) and electrochemical test. SEM images show that the size of nanoflake BMO is about 50 ~ 200 nm. PL and electrochemical analysis show that the nanoflake BMO has a lower recombination rate of photogenerated carriers than particle BMO. The photocatalytic degradation of tetracycline hydrochloride (TC) by nanoflake BMO under visible light is investigated. The results show that the nanoflake BMO-3 has the highest degradation efficiency under visible light, and the degradation efficiency reached 75 % within 120 min, attributed to the unique hierarchical structure, efficient carrier separation and sufficient free radicals to generate active center synergies. The photocatalytic reaction mechanism of TC degradation on the nanoflake BMO is proposed.

Tetracycline is one of the most commonly used as antibiotics for the livestock industry and it is still widely used nowadays. Tetracycline and its metabolites are excreted with excrement, which is difficult to completely removed with conventional sewage treatment, therefore it is apprehended that the tetracycline-resistant bacteria occurs. In this study, the oxidant named ferrate(VI) was used to degrade the tetracycline and investigate the reaction between ferrate(VI) and tetracycline under various aqueous conditions. The highest degradation efficiency of tetracycline occurred in basic condition (pH 10.1 ± 0.1) because of the pKa values of tetracycline and ferrate(VI). The results also showed the effect of water temperature on the degradation of tetracycline was not significant. In addition, the dosage of ferrate(VI) was higher, the degradation of tetracycline and the self-degradation of ferrate(VI) also higher, finally the efficiency of ferrate(VI) was lower. The results said that the various mechanisms effects the reaction of ferrate(VI) oxidation, it required the consideration of the characteristics of the target compound for optimal degradation efficiency. Additionally, intermediate products were detected with LC/MS/MS and three degradation pathways were proposed.

Tetracycline is one of the most commonly used antibiotics in domestic and foreign livestock industries to suppress the growth of pathogens. Tetracycline has been reported as a non-biodegradable compound. Therefore it has been not completely removed in the sewage treatment process. In this study, tetracycline was degraded using liquid ferrate (VI). Based on these experiments, the optimal water condition (pH and water temperature) were selected, appropriate liquid ferrate (VI) dosage was calculated, and finally the degradation pathway was estimated with the intermediate products detected by LC/MS/MS. All degradation experiments were completed within 30 seconds and the optimal condition was obtained in basic condition (pH 10) at room temperature (20℃). And the appropriate molar ratio between tetracycline and liquid ferrate (VI) was 12.5:1. Finally, 12 intermediate products were detected with LC/MS/MS and the degradation pathways and the degradation pathways and proposed the degradation pathways.

In this study, to further understand the mechanism of animal growth and to develop a miniature transgenic animal model, we constructed and tested tetracycline-inducible RNAi system using shRNA targeting the mRNA of mouse insulin-like growth factor (mIGF-1) or mouse growth hormone receptor (mGHR) gene. Quantitative real-time PCR analysis of mouse liver cell (Hepa1c1c7) cells transfected with these vectors showed 85% or 90% of expression inhi-bition effect of IGF-1 or GHR, respectively. In ELISA analysis, the protein level of IGF-1 in the cells expressing the shRNA targeting IGF-1 mRNA was reduced to 26% of non-transformed control cells. Unexpectedly, in case of using shRNA targeting GHR, the IGF-1 protein level was decreased to 75% of control cells. Further experiments are needed to explain the lower interference effect of GHR shRNA in IGF-1 protein. Accumulated knowledge of this approach could be applicable to a variety of related biological area including gene function study, gene therapy, development of miniature animals, etc.

Streptococci are among the normal human microflora that populate the oral cavity. However, oral streptococci are known as a major causative agent for dental caries and bacterial endocarditis. Tetracycline is a broad-spectrum antibiotic that is used for oral infections but two mechanisms of tetracycline resistance in streptococci have been reported. The tet(K) and tet(L) genes in these bacteria are related to the active efflux of tetracycline, whereas tet(M) and tet(O) confer ribosomal protection from this antibiotic. It has been reported that the tetracycline resistance of streptococci is related mainly to the activity of tet(M) and tet(O). In our present study, we examined the prevalence of tet(M) and tet(O) in oral streptococci isolated from Korean dental plaques using PCR. One hundred and forty eight of 635 isolates (23.3%) were tetracycline resistant; 68 of these strains (46%) harbored tet(M) and 3 strains (2%) were positive for tet(O). However, tet(M) and tet(O) did not co-exist in any of the resistant strains. Seventy seven of the 148 tetracycline resistant strains (52%) were negative for both the tet(M) and tet(O) genes.

Until recently the most popular tetracycline-inducible gene expression system has been the one developed by Gossen and Bujard. In this study, we tested the latest version of same system and the results are summarized as follows: Compared with previous one, the difference of new system are minor changes of nucleotide sequences in transactivator and tetracycline response element (TRE) regions. Sensitivity to the doxycycline (a tetracycline derivative) was improved. Leakiness of GFP marker gene expression in non-inducible condition was significantly decreased. Higher expression of the marker gene was observed when the cells were fed with doxycycline- containing medium. Optimal insertion site of woodchuck posttranscriptional regulatory element (WPRE) sequence which was known to increase gene expression was different depending on the origin of cells. In chicken embryonic fibroblast, location of WPRE sequence at 3’ end of TRE resulted in the highest GFP expression. In bovine embryonic fibroblasts, 3’ end of transactivator was the best site for the GFP expression.

Chicken Insulin-like Growth Factor-1 (cIGF-1), one of the most important hormone for regulating physiological function includes body growth, muscle volume, bone density, chicken cell development and metabolism. In order to find in vitro Knokdown expression of cIGF-1, this study introduced tetracycline inducible RNA interference expression system (TetRNAi system). Tet system can inductively control high expression of extrinsic genes and expression of intrinsic genes. So it has advantages such as minimized physiological side-effects any cell and low cytotoxicity. RNAi system is proving to be a powerful experimental tool for inhibition of gene expression and post-transcriptional mechanism of gene silencing. RNAi is mediated by small interfering RNA (siRNA) consisting of 19- to 23- nucleotide double-stranded RNA duplexes that promote specific endonucleolytic cleavage of mRNA targets through an RNA-induced silencing. Then, this study RNAi-based gene knockdown can be achieved by retroviral-based expression systems. Stable integration of our inducible siRNA vector allowed the production of siRNA on doxycycline induction, followed by specific down regulation of chicken IGF-1 gene. Analyses of Real-time PCR to determine expression of the cIGF-1 gene showed successful from chicken embronic fibroblast (CEF) cells with the reduced rate of an approximately 92%. Our results demonstrate the successful regulation of cIGF-1 knockdown expression in CEF cells and support the application of an tetracycline inducible RNAi expression system in transgenic Mini chicken production. This research was supported by Bio-industry Technology Development Program, Ministry for Food, Agriculture, Forestry and Fisheries, Republic of Korea.

Antibiotic resistance in animal isolates of enterococci is a public health concern, because of the risk of transmission of antibiotic-resistant strains or resistance genes to humans through the food chain. This study investigated phenotypic and genotypic resistances profile of tetracycline in 245 Enterococcus isolates from bovine milk. A total of 245 enterococci were isolated from 950 milk samples. The predominant strain was E. faecalis (n = 199, 81.2%) and E. faecium (n = 25, 10.2%). E. avium (n = 7, 2.9%), E. durans (n = 6, 2.5%), E. gallinarum (n = 4, 1.6%), and E. raffinosus (n = 4, 1.6%) were also isolated. Of the 245 enterococcal isolates 76.3% (n = 187) displayed tetracycline resistance (≥ 16 μg/ml). Of the 187 tetracycline-resistant isolates, 83.4% (n = 156), 16.1% (n = 30), and 26.7% (n = 50) possessed the genes tet(M), tet(L), tet(S) respectively. While 3.2% (n = 6) of the tetracycline- resistant isolates possessed all three genes tet(M) + tet(L) + tet(S), 8.6% (n = 16), 16.0% (n = 30), and 2.7% (n = 5) of them possessed two genes tet(M) + tet(L), tet(M) + tet(S), and tet(L) + tet(S) respectively. The tetracycline resistance pattern investigated in this study was attributable mainly to the presence of tet(M).

In this study we tried to construct a more efficient tetracycline-inducible gene expression system by replacing previous key elements with more advance ones. At the beginning, we substituted PGK (phophoglycerate kinase) promoter for CMV (cytomegalovirus) promoter to control “rtTA2sM2” which has been known for high induction efficiency in response to tetracycline. With this modification, expression of the EGFP marker gene under the induction condition was significantly increased. Next, we replaced “TRE” fragment with a modified version named “TRE- tight” which has been reported to have higher affinity and specificity to the transactivator by minor base change of the “TRE” DNA fragment sequence. Use of “TRE-tight” instead of “TRE” resulted in more than 10 fold increment in terms of induction efficiency and significant decrement of background expression in non-inducible condition. By combining PGK promoter and “TRE-tight” fragment, we could upgrade previous tetracycline-inducible system to show more stringent turn on/off gene switch ability and stronger expression of the gene of our interest. Use of this newly developed system must be very helpful to the studies of gene expression, especially to the transgenic animal study in which non-controllable constitutive expression of the transgene has been one of the urgent problems to be solved.