Construction of luminescent Escherichia coli via expressing lux operons and their application on toxicity test.

Recombinant luminescent Escherichia coli strains could be used to detect the toxicity of pure or mixed contaminants as a light-off sensor. In this work, the lux operon of Photobacterium phosphoreum T3 was identified for the first time. Recombinant luminescent E. coli strains were constructed via expressing the lux operons of P. phosphoreum T3 and Vibrio qinghaiensis Q67 in E. coli MG1655, and the optimal protectant containing 10% (w/v) trehalose and 4% sucrose was used to prepare the freeze-dried recombinant luminescent E. coli cells. Then, these freeze-dried E. coli cells were subjected to acute toxicity detection. The results showed that luminescent E. coli strains displayed sensitive toxic responses to BPA, nFe2O3, Cd, Pb, As, and Hg, for example, the EC50 values of BPA and nFe2O3 to luminescent E. coli strains ranged from 1.54 to 50.19 mg/l and 17.50 to 21.52 mg/l, respectively. Indeed, luminescent E. coli strains exhibited more sensitive responses to Cd, Pb, and Hg than the natural strain Q67. The results suggested that recombinant luminescent E. coli strains could be used for the detection of acute toxicity. Furthermore, the combined toxicities of BPA and nFe2O3, Hg, and Pb were measured, and the joint effects of these mixtures were evaluated with luminescent E. coli. The results indicated that the joint effects of BPA and nFe2O3 suggested to be synergistic or additive to luminescent E. coli, while the joint effects of heavy metals and nFe2O3 exhibited additivities. The cellular endocytosis for Fe2O3 nanoparticles was not observed, which could explain the additive instead of synergistic effects between heavy metals and nFe2O3. KEY POINTS: • Sequence of the lux operon from P. phosphoreum T3 was reported for the first time. • Recombinant luminescent E. coli was more sensitive to Cd, Pb, and Hg than Q67. • Joint effects of BPA and nFe2O3 were synergistic or additive to luminescent E. coli.

Preparation of freeze-dried bioluminescent bacteria and their application in the detection of acute toxicity of bisphenol A and heavy metals.

Current chemical analysis approaches for contaminants have failed to reveal their biotoxicity. Moreover, conventional bioassays are time consuming and exhibit poor repeatability. In this study, we performed the acute toxicity detection of various contaminants (chromium (Cr), cadmium (Cd), lead (Pb), arsenic (As), mercury (Hg), tin (Sn), nickel (Ni), and bisphenol A (BPA)) with four bioluminescent bacteria (Vibrio qinghaiensis Q67, V. fischeri, Photobacterium phosphoreum T3, and P. phosphoreum 502) using a rapid, flexible, and low-cost bioassay. We found that the temperature affected the bacterial luminescence, and freeze-dried cells exhibited sensitive toxic responses to contaminants. Indeed, the optimized protectants containing 12% (w/v) trehalose, 4% sucrose, and 2% sorbitol displayed better luminescence and toxic sensitivity. Furthermore, freeze-dried powders of these strains were prepared and subjected to acute toxicity detection. The results showed that all contaminants exhibited acute toxicity toward Q67, but the other strains did not show obvious response to nickel and tin. The relative half-maximal effective concentration (EC50) values of BPA, Cr, Cd, Pb, As, Hg, Ni, and Sn to Q67 were 0.674, 1.313, 11.137, 5.921, 4.674, 0.911, 5.941, and 54.077 mg/L, respectively. In addition, the EC50 values of contaminants toward different strains were suggested to be statistically significant. Freeze-dried Q67 exhibited toxic responses to more contaminants than the other bioluminescent strains; therefore, Q67 was selected to be more suitable than the other strains for single and mixture toxicity detection tests. Compared with other strains, Q67 was more appropriate for the rapid screening of the mixture toxicity of contaminants in samples as a nonspecific screening sensor before the use of standard analysis approaches.

Acute and Chronic Toxicity of Binary Mixtures of Bisphenol A and Heavy Metals.

Bisphenol A (BPA) and heavy metals are widespread contaminants in the environment. However, the combined toxicities of these contaminants are still unknown. In this study, the bioluminescent bacteria Vibrio qinghaiensis Q67 was used to detect the single and combined toxicities of BPA and heavy metals, then the joint effects of these contaminants were evaluated. The results show that chronic toxicities of chromium (Cr), cadmium (Cd), lead (Pb), arsenic (As), mercury (Hg), nickel (Ni), and BPA were time−dependent; in fact, the acute toxicities of these contaminants were stronger than the chronic toxicities. Furthermore, the combined toxicities of BPA and heavy metals displayed BPA + Hg > BPA + Cr > BPA + As > BPA + Ni > BPA + Pb > BPA + Cd in the acute test and BPA + Hg > BPA + Cd > BPA + As > BPA + Cd in the chronic test, which suggested that the combined toxicity of BPA and Hg was stronger than that of other mixtures in acute as well as chronic tests. Additionally, both CA and IA models underestimated the toxicities of mixtures at low concentrations but overestimated them at high concentrations, which indicates that CA and IA models were not suitable to predict the toxicities of mixtures of BPA and heavy metals. Moreover, the joint effects of BPA and heavy metals mainly showed antagonism and additive in the context of acute exposure but synergism and additive in the context of chronic exposure. Indeed, the difference in the joint effects on acute and chronic exposure can be explained by the possibility that mixtures inhibited cell growth and luminescence in chronic cultivation. The chronic toxicity of the mixture should be considered if the mixture results in the inhibition of the growth of cells.

Fluorescent indicators for live-cell and in vitro detection of inorganic cadmium dynamics.

Cadmium contamination is a severe threat to the environment and food safety. Thus, there is an urgent need to develop highly sensitive and selective cadmium detection tools. The engineered fluorescent indicator is a powerful tool for the rapid detection of inorganic cadmium in the environment. In this study, the development of yellow fluorescent indicators of cadmium chloride by inserting a fluorescent protein at different positions of the high cadmium-specific repressor and optimizing the flexible linker between the connection points is reported. These indicators provide a fast, sensitive, specific, high dynamic range, and real-time readout of cadmium ion dynamics in solution. The excitation and emission wavelength of this indicator used in this work are 420/485 and 528 nm, respectively. Fluorescent indicators N0C0/N1C1 showed a linear response to cadmium concentration within the range from 10/30 to 50/100 nM and with a detection limit of 10/33 nM under optimal condition. Escherichia coli cells containing the indicator were used to further study the response of cadmium ion concentration in living cells. E. coli N1C1 could respond to different concentrations of cadmium ions. This study provides a rapid and straightforward method for cadmium ion detection in vitro and the potential for biological imaging.

Terahertz Chiral Metamaterials Enabled by Textile Manufacturing.

Easy-to-fabricate, large-area, and inexpensive microstructures that realize control of the polarization of terahertz (THz) radiation are of fundamental importance to the development of the field of THz wave photonics. However, due to the lack of natural materials that can facilitate strong THz radiation-matter interactions, THz polarization components remain an undeveloped technology. Strong resonance-based responses offered by THz metamaterials have led to the recent development of THz metadevices, whereas, for polarization control devices, micrometer-scale fabrication techniques including aligned photolithography are generally required to create multilayer microstructures. In this work, leveraging a two-step textile manufacturing approach, a chiral metamaterial capable of exhibiting strong chiroptical responses at THz frequencies is demonstrated. Chiral-selective transmission and pronounced optical activity are experimentally observed. In sharp contrast to smart-clothing-related devices (e.g., textile antennas), the investigated chiral metamaterials gain their THz properties directly from the yarn-twisting enabled microhelical strings. It is envisioned that the interplay between meta-atom designs and textile manufacturing technology will lead to a new family of metadevices for complete control over the phase, amplitude, and polarization of THz radiation.

Engineering the regulatory site of the catalase promoter for improved heterologous protein production in Pichia pastoris.

OBJECTIVES: To build a stronger Pichia pastoris PCAT1 promoter and to identify putative transcriptional factor binding sites (TFBSs) on PCAT1 that affect the activity of the promoter. RESULT: A synthetic library of PCAT1 was generated by deleting or duplicating putative TFBS motifs in the promoter sequence. CSRE, MIG1, RAP1 and HAP2/3/4 were found to have important effects on PCAT1 activity. The PCAT1 variant P4 with a putative binding site of RAP1 on the promoter sequence showed a stronger activity compared with that of the wild-type PCAT1 and PAOX1, which is the strongest natural P. pastoris promoter that has been reported. This inference was confirmed with EGFP (enhanced green fluorescent protein) and Candida Antarctica lipase B as the reporters. CONCLUSION: The role of the transcriptional regulator RAP1 may be important in PCAT1 methanol induction. A stronger PCAT1 variant can be constructed by the duplication of the putative binding site of RAP1 on the PCAT1 promoter sequence. This PCAT1 variant has potential value for heterologous protein production, metabolic engineering, and synthetic biology.

[Clinical characteristics for connective tissue disease complicated with cryptococcal meningitis].

OBJECTIVE: To investigate the clinical characteristics and prognosis for connective tissue disease (CTD) with cryptococcal meningitis (CM). 
 Methods: Clinical data of 18 patients with CTD complicated with cryptococcal meningitis diagnosed by Rheumatology and Immunology Department, Xiangya Hospital, Central South University from January 2000 to January 2017, were retrospectively analyzed.
 Results: The common symptoms of CTD patients with CM were headache, fever, nausea, and vomiting. Patients with severe clinical manifestations, such as convulsions and disturbance of consciousness, all died. Logistic regression analysis showed that disturbance of consciousness and decreased peripheral blood lymphocyte count might be the related factors of poor prognosis of CTD patients with CM (P<0.05). The mortality rate of CTD with CM was 61.11%, and the effective rate of treatment for this disease was 38.89%.
 Conclusion: CTD patients with cryptococcal meningitis have a high risk of death. Severe clinical symptoms, such as disturbance of consciousness and lower peripheral blood lymphocyte count, are associated with its poor prognosis.

Coexistence of systemic sclerosis and ankylosing spondylitis: A case report and literature review.

Systemic sclerosis (SSc) is an autoimmune disease characterized by thickening of the skin and organ fibrosis. Ankylosing spondylitis (AS) is a type of arthritis with long-term inflammation of the axial joints. Previous studies presented 5 cases of concomitant AS and SSc. However, there was only 1 patient of those 5 cases complaining of muscle weakness while all patients had approximately normal creatine kinase (CK). Here we reported a young male who met the criteria for SSc and AS while showing significantly elevated CK. Human leukocyte antigen (HLA) typing results indicated the genetic susceptibility to these two diseases. The patient was prescribed prednisone (30 mg/d) and cyclophosphamide. After 2 months, the patient's skin became soft with normal CK.