UV-filter benzophenones suppress human, pig, rat, and mouse 11ß-hydroxysteroid dehydrogenase 1: Structure-activity relationship and in silico docking analysis.

Benzophenone chemicals (BPs) have been developed to prevent the adverse effects of UV radiation and they are widely contaminated. 11ß-Hydroxysteroid dehydrogenase 1 (11ß-HSD1) catalyze the conversion of inactive glucocorticoid to active glucocorticoid, playing critical role in many physiological function. However, the direct effect of BPs on human, pig, rat, and mouse 11ß-HSD1 remains unclear. In this study, we screened the inhibitory strength of 12 BPs on 4 species, and performed the structure-activity relationship (SAR) and in silico docking analysis. The inhibitory potency of BPs was: for human 11ß-HSD1, BP6 (IC50 = 18.76 µM) > BP8 (40.84 µM) > BP (88.89 µM) > other BPs; for pig 11ß-HSD1, BP8 (45.57 µM) > BP6 (59.44 µM) > BP2 (65.12 µM) > BP (135.56 µM) > other BPs; for rat 11ß-HSD1, BP7 (67.17 µM) > BP (68.83 µM) > BP8 (133.04 µM) > other BPs; and for mouse 11ß-HSD1, BP8 (41.41 µM) > BP (50.61 µM) > other BPs. These BP chemicals were mixed/competitive inhibitors of these 11ß-HSD1 enzymes. The 2,2'-dihydroxy substitutions in two benzene rings play a key role in enhancing the effectiveness of inhibiting 11ß-HSD1, possibly via increasing hydrogen bond interactions. Docking analysis shows that these BPs bind to NADPH/glucocorticoid binding sites and forms hydrogen bonds with catalytic residues Ser and/or Tyr. In conclusion, this study demonstrates that BP chemicals can inhibit 11ß-HSD1 from 4 species, and there are subtle species-dependent difference in the inhibitory strength and structural variations of BPs.

Demethoxylation of curcumin enhances its inhibition on human and rat 17ß-hydroxysteroid dehydrogenase 3: QSAR structure-activity relationship and in silico docking analysis.

Curcuminoids have many pharmacological effects. They or their metabolites may have side effects by suppressing 17ß-hydroxysteroid dehydrogenase 3 (17ß-HSD3). Herein, we investigated the inhibition of curcuminoids and their metabolites on human and rat 17ß-HSD3 and analyzed their structure-activity relationship (SAR) and performed in silico docking. Curcuminoids and their metabolites ranked in terms of IC50 values against human 17ß-HSD3 were bisdemethoxycurcumin (0.61 µM) > curcumin (8.63 µM) > demethoxycurcumin (9.59 µM) > tetrahydrocurcumin (22.04 µM) > cyclocurcumin (29.14 µM), and those against rat 17ß-HSD3 were bisdemethoxycurcumin (3.94 µM) > demethoxycurcumin (4.98 µM) > curcumin (9.62 µM) > tetrahydrocurcumin (45.82 µM) > cyclocurcumin (143.5 µM). The aforementioned chemicals were mixed inhibitors for both enzymes. Molecular docking analysis revealed that they bind to the domain between the androstenedione and NADPH active sites of 17ß-HSD3. Bivariate correlation analysis showed a positive correlation between LogP and pKa of curcumin derivatives with their IC50 values. Additionally, a 3D-QSAR analysis revealed that a pharmacophore model consisting of three hydrogen bond acceptor regions and one hydrogen bond donor region provided a better fit for bisdemethoxycurcumin compared to curcumin. In conclusion, curcuminoids and their metabolites possess the ability to inhibit androgen biosynthesis by directly targeting human and rat 17ß-HSD3. The inhibitory strength of these compounds is influenced by their lipophilicity and ionization characteristics.

Bisphenol a alternatives suppress human and rat aromatase activity: QSAR structure-activity relationship and in silico docking analysis.

The use of alternative substances to replace bisphenol A (BPA) has been encouraged. The objective of this study was to evaluate the effects of BPA and 9 BPA alternatives on human and rat aromatase (CYP19A1) in human and rat placental microsomes. The results revealed that bisphenol A, AP, B, C, E, F, FL, S, and Z, and 4,4'-thiodiphenol (TDP) inhibited human CYP19A1 and bisphenol A, AP, B, C, FL, Z, and TDP inhibited rat CYP19A1. The IC50 values of human CYP19A1 ranged from 3.3 to 172.63 µM and those of rat CYP19A1 ranged from 2.20 to over 100 µM. BPA alternatives were mixed/competitive inhibitors and inhibited estradiol production in BeWo placental cells. Molecular docking analysis showed that BPA alternatives bind to the domain between heme and steroid and form a hydrogen bond with catalytic residue Met374. Pharmacophore analysis showed that there were one hydrogen bond donor, one hydrophobic region, and one ring aromatic hydrophobic region. Bivariate correlation analysis showed that molecular weight, alkyl atom weight, and LogP of BPA alternatives were inversely correlated with their IC50 values. In conclusion, BPA alternatives can inhibit human and rat CYP19A1 and the lipophilicity and the substituted alkyl size determines their inhibitory strength.

Enhanced inhibition of human and rat aromatase activity by benzene ring substitutions in bisphenol A: QSAR structure-activity relationship and in silico docking analysis.

Bisphenol A (BPA) is a widely used plastic material, but its potential endocrine disrupting effect has restricted its use. The BPA alternatives have raised concerns. This study aimed to compare inhibitory potencies of 11 BPA analogues on human and rat placental aromatase (CYP19A1). The inhibitory potency on human CYP19A1 ranged from bisphenol H (IC50, 0.93 µM) to tetramethyl BPA and tetrabromobisphenol S (ineffective at 100 µM) when compared to BPA (IC50, 73.48 µM). Most of them were mixed/competitive inhibitors and inhibited estradiol production in human BeWo cells. Molecular docking analysis showed all BPA analogues bind to steroid active site or in between steroid and heme of CYP19A1 and form a hydrogen bond with catalytic residue Met374. Pharmacophore analysis showed that there were 4 hydrophobic regions for BPA analogues, with bisphenol H occupying 4 regions. Bivariate correlation analysis showed that LogP (lipophilicity) and LogS (water solubility) of BPA analogues were correlated with their IC50 values. Computerized drug metabolism and pharmacokinetics analysis showed that bisphenol H, tetrabromobisphenol A, and tetrachlorobisphenol A had low solubility, which might explain their weaker inhibition on estradiol production on BeWo cells. In conclusion, BPA analogues mostly can inhibit CYP19A1 and the lipophilicity determines their inhibitory strength.

Azole fungicides inhibit human and rat gonadal 3ß-hydroxysteroid dehydrogenases: Structure-activity relationship and in silico docking analysis.

Azole fungicides are widely used in the agricultural industry to control fungal infections in crops. However, recent studies have shown that some azole fungicides inhibit the activity of 3ß-hydroxysteroid dehydrogenases (3ß-HSDs) in the gonads. Out of the 16 azole fungicides tested, 8 were found to inhibit human KGN cell 3ß-HSD2 with IC50 values of less than 100 µM. The strongest inhibitor was difenoconazole, with an IC50 value of 1.88 µM. In contrast, only 3 of the azole fungicides inhibited rat testicular 3ß-HSD1, which was less sensitive to inhibition. Azole fungicides potently inhibited progesterone secretion by KGN cells under basal and forskolin stimulated conditions at ≥ 5 µM. The inhibitory strength of azole fungicides was determined by their lipophilicity (LogP), molecular weight, pKa, and binding energy. A pharmacophore analysis revealed that the hydrogen bond acceptor-lipid group was a critical feature required for inhibition. Overall, these findings suggest that the use of azole fungicides have unintended consequences on reproductive health due to their inhibition of gonadal 3ß-HSDs. Key words: Azole fungicides; steroid hormones; 3ß-hydroxysteroid dehydrogenase; docking analysis; lipophilicity.

Characterization of a Riboflavin-Producing Mutant of Bacillus subtilis Isolated by Droplet-Based Microfluidics Screening.

Bacillus subtilis is one of the commonly used industrial strains for riboflavin production. High-throughput screening is useful in biotechnology, but there are still an insufficient number of articles focusing on improving the riboflavin production of B. subtilis by this powerful tool. With droplet-based microfluidics technology, single cells can be encapsulated in droplets. The screening can be carried out by detecting the fluorescence intensity of secreted riboflavin. Thus, an efficient and high-throughput screening method suitable for riboflavin production strain improvement could be established. In this study, droplet-based microfluidics screening was applied, and a more competitive riboflavin producer U3 was selected from the random mutation library of strain S1. The riboflavin production and biomass of U3 were higher than that of S1 in flask fermentation. In addition, the results of fed-batch fermentation showed that the riboflavin production of U3 was 24.3 g/L, an 18% increase compared with the parent strain S1 (20.6 g/L), and the yield (g riboflavin/100 g glucose) increased by 19%, from 7.3 (S1) to 8.7 (U3). Two mutations of U3 (sinRG89R and icdD28E) were identified through whole genome sequencing and comparison. Then they were introduced into BS168DR (parent of S1) for further analysis, which also caused riboflavin production to increase. This paper provides protocols for screening riboflavin-producing B. subtilis with droplet-based microfluidics technology and reveals mutations in riboflavin overproduction strains.

Integrated Urinalysis Devices Based on Interface-Engineered Field-Effect Transistor Biosensors Incorporated With Electronic Circuits.

Urinalysis is attractive in non-invasive early diagnosis of bladder cancer compared with clinical gold standard cystoscopy. However, the trace bladder tumor biomarkers in urine and the particularly complex urine environment pose significant challenges for urinalysis. Here, a clinically adoptable urinalysis device that integrates molecular-specificity indium gallium zinc oxide field-effect transistor (IGZO FET) biosensor arrays, a device control panel, and an internet terminal for directly analyzing five bladder-tumor-associated proteins in clinical urine samples, is reported for bladder cancer diagnosis and classification. The IGZO FET biosensors with engineered sensing interfaces provide high sensitivity and selectivity for identification of trace proteins in the complex urine environment. Integrating with a machine-learning algorithm, this device can identify bladder cancer with an accuracy of 95.0% in a cohort of 197 patients and 75 non-bladder cancer individuals, distinguishing cancer stages with an overall accuracy of 90.0% and assessing bladder cancer recurrence after surgical treatment. The non-invasive urinalysis device defines a robust technology for remote healthcare and personalized medicine.

[Upgrading microbial strains for fermentation industry].

Fermentation is a green, low-carbon and sustainable process for the production of food, chemicals, fuels, and materials by using microbial strains as biocatalysts and renewable resources such as starch and biomass as feedstocks. China has the world's largest fermentation industry, the scale of amino acids, vitamins, and some other fermentation products accounted for 60%-80% of the global market share. The development of fermentation industry is of great significance for the strategic goal of "carbon neutralization and carbon peak" and the development of bioeconomy. Microbial strains are the core of fermentation industry, which directly decide what kind of chemical can be produced from what kind of feedstock at what cost. Innovating industrial strains to improve the conversion efficiency of raw materials, increase the production level, and expand product portfolio is the key to the high-quality development of fermentation industry. In recent years, the development of synthetic biology and systems biology has further deepened the understanding of the physiological and metabolic mechanisms of microbial chassis and accelerated the development of gene editing and other enabling technologies for strain design and engineering. All these advances have provided new driving force for the upgrading of industrial strains. This review focused on the representative fermentation products including amino acids, B vitamins, citric acid, and bio-ethanol. The latest progress of strain development for fermentation industry was reviewed from the perspective of basic research and technology innovation for industrial microbial chassis. How the integration of artificial intelligence and automation with life science will reshape the upgrading of industrial strains was also discussed.

Improving the Production of Riboflavin by Introducing a Mutant Ribulose 5-Phosphate 3-Epimerase Gene in Bacillus subtilis.

Ribulose 5-phosphate (Ru5P) and guanosine 5'-triphosphate (GTP) are two key precursors of riboflavin, whereby Ru5P is also a precursor of GTP. Ribulose 5-phosphate 3-epimerase (Rpe) catalyzes the conversion of ribulose 5-phosphate into xylulose 5-phosphate. Inactivation of Rpe can reduce the consumption of Ru5P, enhancing the carbon flux toward riboflavin biosynthesis. Here we investigated the effect of mutation of rpe and other related genes on riboflavin production, physiological and metabolic phenotypes in Bacillus subtilis LY (BSLY). Introducing single nucleotide deletion (generated BSR) or nonsense mutation (generated BSRN) on the genomic copy of rpe, resulting in more than fivefold increase of riboflavin production over the parental strain. BSR process 62% Rpe activity, while BSRN lost the entire Rpe activity and had a growth defect compared with the parent strain. BSR and BSRN exhibited increases of the inosine and guanine titers, in addition, BSRN exhibited an increase of inosine 5'-monophosphate titer in fermentation. The transcription levels of most oxidative pentose phosphate pathway and purine synthesis genes were unchanged in BSR, except for the levels of zwf and ndk, which were higher than in BSLY. The production of riboflavin was increased to 479.90 ± 33.21 mg/L when ribA was overexpressed in BSR. The overexpression of zwf, gntZ, prs, and purF also enhanced the riboflavin production. Finally, overexpression of the rib operon by the pMX45 plasmid and mutant gnd by pHP03 plasmid in BSR led to a 3.05-fold increase of the riboflavin production (977.29 ± 63.44 mg/L), showing the potential for further engineering of this strain.

Study of the Characteristics of Two Immobilized Microbial Materials in Degradation and Evolution of Petroleum Hydrocarbon.

To enhance the degradation efficiency of oily wastewater, polyacrylamide (PAM)-sodium alginate (SA) and poly(vinyl alcohol) (PVA)-sodium alginate (SA) were mixed and used as spherical supporting materials for the immobilization of microbials, which were employed as a platform to study the degradation of total petroleum hydrocarbons (TPHs) in the oily wastewater. The degradation and evolution of normal paraffin (n-paraffin) series have been studied by determining the crude oil group composition of the residual oils by the gas chromatography-mass spectrometry (GC-MS) analysis. The results show that the half-lives of the PAM-SA-immobilized microorganisms are 6.21 days, which is 2.11 days less than that of PVA-SA, indicating that more nutrients are provided by PAM-SA for microbial growth, which can accelerate the degradation of TPHs. As can be seen from the GC-MS analysis, the main peak carbons of the n-paraffin series are moved backward after 14 days of degradation, implying the degrading advantage of n-paraffin with low carbon numbers. The ∑C21-/∑C22+ value of PAM-SA was measured to be 0.749, which is greater than that of PVA-SA (0.051), indicating that PAM-SA has a superior ability to degrade normal paraffins with high carbon numbers. After 14 days of degradation, an odd-even predominance (OEP) (the mass ratio of normal alkanes of odd carbon/even carbon) value of 1.075 for PAM-SA was obtained, which is slightly larger than that of PVA-SA (0.967), indicating a better degradation performance of PAM-SA, especially for the degradation of the even-carbon normal paraffins with high carbon numbers. The Pr/Ph of PAM-SA is 0.938, which is also greater than that of PVA-SA (0.844), indicating that the ability of PAM-SA for the degradation of isoprenoids is superior to that of PVA-SA under the immobilized conditions. Based on these results, in terms of immobilization of microorganisms, PAM-SA, instead of PVA-SA, is more advantageous for the degradation of TPH in the oily wastewater.

[Expression and significance of Ki-67, PI3K and Beclin1 in oral squamous cell carcinoma].

PURPOSE: To detect the expression and significance of Ki-67, PI3K and Beclin1 in oral squamous cell carcinoma (OSCC). METHODS: Thirty patients with OSCC admitted to Nanjing Stomatology Hospital from January 2017 to December 2018 were selected. All specimens were harvested and treated with immunohistochemical staining. The expressions of Ki-67, PI3K and Beclin 1 were detected. Pearson's correlation was used to analyze the correlation among TMSG-1, Ki-67 and Pgp1.The data were analyzed with SPSS 20.0 software package. RESULTS: The positive rates of Ki-67 and PI3K in OSCC tissues were significantly higher than those in adjacent tissues, and the positive rates of Beclin1 were significantly lower than those in adjacent tissues (P<0.05). The positive expression rates of Ki-67, PI3K and Beclin1 in highly differentiated OSCC were significantly higher than those in moderately differentiated and poorly differentiated OSCC (P<0.05). The positive expression rates of Ki-67 and PI3K in OSCC with lymph node metastasis were significantly higher than those in OSCC without lymph node metastasis. The positive expression rates of Beclin1 in OSCC with lymph node metastasis were significantly lower than those in OSCC without lymph node metastasis (P<0.05). The positive expression rates of Ki-67, PI3K and Beclin1 in stageⅠ+Ⅱ and Ⅲ+Ⅳ OSCC were not significantly different (P>0.05). Ki-67 was positively correlated with PI3K (r=0.391, P=0.032), Ki-67 was negatively correlated with Beclin1 (r=-0.525, P=0.02), and Beclin1 was negatively correlated with PI3K(r=-0.367, P=0.045). CONCLUSIONS: Ki-67, PI3K and Beclin1 are correlated with lymph node metastasis and pathological staging. They may be involved in the occurrence and development of OSCC.

Superhydrophilic and Oleophobic Porous Architectures Based on Basalt Fibers as Oil-Repellent Photothermal Materials for Solar Steam Generation.

The construction of efficient solar steam generation systems is of great importance for a range of purposes, such as desalination, distillation, and sterilization. In this study, superhydrophilic and oleophobic porous architectures are prepared by carbonization of a mixture of basalt fibers and tissue paper (BFT) followed by an oleophobic modification (O-BFT) to form oil-repellent photothermal materials for efficient solar steam generation. The as-prepared O-BFT shows high porosity, superior light absorption, and good thermal insulation (thermal conductivity=0.371 Wm-1 K-1 ). Correspondingly, a high solar energy conversion efficiency of 90 % is achieved with 1 sun irradiation. Its strong oleophobic wettability endows it with excellent oil-repellent ability. Therefore, a high energy conversion efficiency of 81 % in oily water was obtained with 1 sun irradiation, whereas the unmodified BFT only shows a low energy conversion efficiency of 26 % because of severe oil contamination, which significantly blocks water evaporation. These unique features of O-BFT makes enable efficient solar steam generation even in oily wastewater, showing great advantages over reported photothermal materials that display poor antifouling performance, which in turn largely extends its application range for practical solar steam generation.

Video-Based Person Re-Identification by an End-To-End Learning Architecture with Hybrid Deep Appearance-Temporal Feature.

Video-based person re-identification is an important task with the challenges of lighting variation, low-resolution images, background clutter, occlusion, and human appearance similarity in the multi-camera visual sensor networks. In this paper, we propose a video-based person re-identification method called the end-to-end learning architecture with hybrid deep appearance-temporal feature. It can learn the appearance features of pivotal frames, the temporal features, and the independent distance metric of different features. This architecture consists of two-stream deep feature structure and two Siamese networks. For the first-stream structure, we propose the Two-branch Appearance Feature (TAF) sub-structure to obtain the appearance information of persons, and used one of the two Siamese networks to learn the similarity of appearance features of a pairwise person. To utilize the temporal information, we designed the second-stream structure that consisting of the Optical flow Temporal Feature (OTF) sub-structure and another Siamese network, to learn the person's temporal features and the distances of pairwise features. In addition, we select the pivotal frames of video as inputs to the Inception-V3 network on the Two-branch Appearance Feature sub-structure, and employ the salience-learning fusion layer to fuse the learned global and local appearance features. Extensive experimental results on the PRID2011, iLIDS-VID, and Motion Analysis and Re-identification Set (MARS) datasets showed that the respective proposed architectures reached 79%, 59% and 72% at Rank-1 and had advantages over state-of-the-art algorithms. Meanwhile, it also improved the feature representation ability of persons.

Engineering a vitamin B12 high-throughput screening system by riboswitch sensor in Sinorhizobium meliloti.

BACKGROUND: As a very important coenzyme in the cell metabolism, Vitamin B12 (cobalamin, VB12) has been widely used in food and medicine fields. The complete biosynthesis of VB12 requires approximately 30 genes, but overexpression of these genes did not result in expected increase of VB12 production. High-yield VB12-producing strains are usually obtained by mutagenesis treatments, thus developing an efficient screening approach is urgently needed. RESULT: By the help of engineered strains with varied capacities of VB12 production, a riboswitch library was constructed and screened, and the btuB element from Salmonella typhimurium was identified as the best regulatory device. A flow cytometry high-throughput screening system was developed based on the btuB riboswitch with high efficiency to identify positive mutants. Mutation of Sinorhizobium meliloti (S. meliloti) was optimized using the novel mutation technique of atmospheric and room temperature plasma (ARTP). Finally, the mutant S. meliloti MC5-2 was obtained and considered as a candidate for industrial applications. After 7 d's cultivation on a rotary shaker at 30 °C, the VB12 titer of S. meliloti MC5-2 reached 156 ± 4.2 mg/L, which was 21.9% higher than that of the wild type strain S. meliloti 320 (128 ± 3.2 mg/L). The genome of S. meliloti MC5-2 was sequenced, and gene mutations were identified and analyzed. CONCLUSION: To our knowledge, it is the first time that a riboswitch element was used in S. meliloti. The flow cytometry high-throughput screening system was successfully developed and a high-yield VB12 producing strain was obtained. The identified and analyzed gene mutations gave useful information for developing high-yield strains by metabolic engineering. Overall, this work provides a useful high-throughput screening method for developing high VB12-yield strains.

Nicotinamide Phosphoribosyltransferase Upregulation by Phenylephrine Reduces Radiation Injury in Submandibular Gland.

PURPOSE: Radiation therapy for head and neck cancer commonly leads to radiation sialadenitis. Emerging evidence has indicated that phenylephrine pretreatment reduces radiosensitivity in the salivary gland; however, the underlying cytoprotective mechanism remains unclear. Nicotinamide phosphoribosyltransferase (NAMPT) is not only a key enzyme for the nicotinamide adenine dinucleotide salvage pathway, but also a cytokine participating in cell survival, metabolism, and longevity, with a broad effect on cellular functions in physiology and pathology. However, the regulatory events of NAMPT in response to the irradiated salivary gland are unknown. METHODS AND MATERIALS: The cell viability of primary cultured submandibular gland cells was determined using the PrestoBlue assay. NAMPT expression was measured using reverse transcriptase polymerase chain reaction and Western blotting in vitro and in vivo. Silent information regulator 1 (SIRT1) and phosphorylated Akt protein levels were examined by Western blotting. The cellular locations of NAMPT and SIRT1 were detected by immunohistochemistry. NAMPT promoter activity was assessed using the luciferase reporter gene assay. RESULTS: NAMPT was mainly distributed in the cytoplasm of granular convoluted tubule cells and ductal cells in normal submandibular glands. mRNA and protein expression of NAMPT was downregulated after radiation but upregulated with phenylephrine pretreatment both in vivo and in vitro. Moreover, the protein expression of phosphorylated Akt and SIRT1 was decreased in irradiated glands, and phenylephrine pretreatment restored the expression of both. SIRT1 was mainly located in the cell nucleus and cytoplasm in the normal submandibular gland. Phenylephrine dramatically enhanced the expression of SIRT1, which was significantly reduced by radiation. Furthermore, phenylephrine induced a marked increase of NAMPT promoter activity. CONCLUSIONS: These findings reveal the regulatory mechanisms of NAMPT expression, which help to understand the mechanism of the cytoprotective role of phenylephrine on irradiated tissues.

A newly isolated and identified vitamin B12 producing strain: Sinorhizobium meliloti 320.

Vitamin B12 (Cobalamin, VB12) has several physiological functions and is widely used in pharmaceutical and food industries. A new unicellular species was extracted from China farmland, and the strain could produce VB12 which was identified by HPLC and HPLC-MS/MS. 16S rDNA analysis reveals this strain belongs to the species Sinorhizobium meliloti and we named it S. meliloti 320. Its whole genome information indicates that this strain has a complete VB12 synthetic pathway, which paves the way for further metabolic engineering studies. The optimal carbon and nitrogen sources are sucrose and corn steep liquor (CSL) plus peptone. The optimal combination of sucrose and CSL was obtained by response surface methodology as they are the most suitable carbon and nitrogen sources, respectively. This strain could produce 140 ± 4.2 mg L(-1) vitamin B12 after incubating for 7 days in the optimal medium.

Identification and characterization of the chromosomal yefM-yoeB toxin-antitoxin system of Streptococcus suis.

Toxin-antitoxin (TA) systems are widely prevalent in the genomes of bacteria and archaea. These modules have been identified in Escherichia coli and various other bacteria. However, their presence in the genome of Streptococcus suis, an important zoonotic pathogen, has received little attention. In this study, we describe the identification and characterization of a type II TA system, comprising the chromosomal yefM-yoeB locus of S. suis. The yefM-yoeB locus is present in the genome of most serotypes of S. suis. Overproduction of S. suis YoeB toxin inhibited the growth of E. coli, and the toxicity of S. suis YoeB could be alleviated by the antitoxin YefM from S. suis and Streptococcus pneumoniae, but not by E. coli YefM. More importantly, introduction of the S. suis yefM-yoeB system into E. coli could affect cell growth. In a murine infection model, deletion of the yefM-yoeB locus had no effect on the virulence of S. suis serotype 2. Collectively, our data suggested that the yefM-yoeB locus of S. suis is an active TA system without the involvement of virulence.

Whole-cell method for phenol detection based on the color reaction of phenol with 4-aminoantipyrine catalyzed by CotA laccase on endospore surfaces.

A green method for phenol spectrophotometric determination was developed based on the color reaction of phenol with 4-aminoantipyrine catalyzed by addition of Bacillus amyloliquefaciens endospores in the presence of O2. The catalytic activity of the endospores may be attributed to the presence of coat protein A on the cell surfaces. This deduction was confirmed by cotA gene knock-out from B. amyloliquefaciens using the homologous double-exchange method. Under optimal conditions, linear responses were obtained over phenol concentrations ranging from 5.0×10(-5)gL(-1) to 1.0×10(-2)gL(-1) (r=0.9984) with a detection limit of 2.1×10(-5)gL(-1) (3σ). Repeatability measurements of 1.0mgL(-1) phenol provided reproducible results with a relative standard deviation of 5.3% (n=11). Standard addition tests indicated recoveries ranging from 92.78% to 107.60%. The proposed whole-cell method was successfully used to detect total phenol in synthetic samples. Results confirmed the potential use of the developed method in practical applications.