Stomach as the target organ of Rickettsia heilongjiangensis infection in C57BL/6 mice identified by click chemistry.

Spotted fever group rickettsiae (SFGR) are obligate intracellular bacteria that cause spotted fever. The limitations of gene manipulation pose great challenges to studying the infection mechanisms of Rickettsia. By combining bioorthogonal metabolism and click chemistry, we developed a method to label R. heilongjiangensis via azide moieties and achieved rapid pathogen localization without complex procedures. Moreover, we constructed a C57BL/6 mice infection model by simulating tick bites and discovered that the stomach is the target organ of R. heilongjiangensis infection through in vivo imaging systems, which explained the occurrence of gastrointestinal symptoms following R. heilongjiangensis infection in some cases. This study offers a unique perspective for subsequent investigations into the pathogenic mechanisms of SFGR and identifies a potential target organ for R. heilongjiangensis.

Catalytic performance and mechanism study of the isomerization of 2,5-dichlorotoluene to 2,4-dichlorotoluene.

This work investigates the influence of catalyst HZSM-5 on the isomerization of 2,5-dichlorotoluene (2,5-DCT) to produce 2,4-dichlorotoluene (2,4-DCT). We observe that hydrothermal treatment leads to a decrease in total acidity and Brønsted/Lewis ratio of HZSM-5 while generating new secondary pores. These characteristics result in excellent selectivity for post-hydrothermal modified HZSM-5 in the isomerization reaction from 2,5-DCT to 2,4-DCT. Under atmospheric pressure at 350 °C, unmodified HZSM-5 achieves a selectivity of 66.4% for producing 2,4-DCT, however after hydrothermal modification the selectivity increases to 78.7%. Density Functional Theory (DFT) calculations explore the thermodynamic aspects of adsorption between the HZSM-5 surface and 2,4-DCT. The kinetic perspective investigates the mechanism involving proton attack on the methyl group of 2,5-DCT followed by rearrangement leading to formation of 2,4-DCT during isomerization. The consistency between simulation and experimental results provides evidence for the feasibility of isomerizing 2,5-DCT to 2,4-DCT. This work fills the gap in the low value-added product 2,5-DCT isomer conversion, indicating its significant practical application potential and provides a valuable reference and guidelines for industrial research in this field.

Stereoselective Synthesis of Tetrasubstituted Olefins via Visible-Light-Promoted Iodine-Mediated Homo-Coupling of Diazo.

A visible-light-promoted iodine-mediated homo-coupling of diazo was first described. A series of tetrasubstituted olefins were synthesized in high yields and with low to high Z-selectivities from phenyldiazoacetates. For 3-diazooxindoles, isoindigo derivatives were provided in moderate to high yields and with excellent E-selectivities. Experimental results showed that the reaction proceeded through a diiodo intermediate. The synthetic usefulness of this reaction was illustrated by the synthesis of maleimide derivatives and dispiro epoxy.

Untargeted and targeted gingival metabolome in rodents reveal metabolic links between high-fat diet-induced obesity and periodontitis.

AIM: To characterize gingival metabolome in high-fat diet (HFD)-induced obesity in mice with/without periodontitis. METHODS: HFD-induced obesity mouse model was established by 16-week feeding, and a lean control group was fed with low-fat diet (n = 21/group). Both models were induced for periodontitis on the left sides by molar ligation for 10 days, whereas the right sides were used as controls. Gingival metabolome and arginine metabolism were analysed by non-targeted/targeted liquid chromatography-mass spectrometry. RESULTS: Of 2247 reference features, presence of periodontitis altered 165 in lean versus 885 in HFD mice; and HFD altered 525 in absence versus 1435 in presence of periodontitis. Compared with healthy condition, periodontitis and HFD had distinct effects on gingival metabolome. Metabolomic impacts of periodontitis were generally greater in HFD mice versus lean controls. K-medoids clustering showed that HFD amplified the impacts of periodontitis on gingival metabolome in both intensity and extensity. Ten metabolic pathways were enriched, including 2 specific to periodontitis, 5 specific to HFD and 3 shared ones. Targeted validation on arginine metabolism confirmed the additive effects between HFD and periodontitis. CONCLUSION: The obese population consuming excessive HFD display amplified metabolic response to periodontitis, presenting a metabolic susceptibility to exacerbated periodontal destruction.

[Synergistic effects of organic fertilizer coupled with phosphate-solubilizing and nitrogen-fixing bacteria on nutrient characteristics of yellow-brown soil under carbon deficiency]. / æœ‰æœºè‚¥å’Œè§£ç£·å›ºæ°®èŒé æ–½å¯¹ç¼ºç¢³é»„æ£•å£¤å »åˆ†ç‰¹æ€§çš„ååŒæ•ˆåº”.

Understanding the dynamics of phosphate-solubilizing and N2-fixing bacteria on soil nutrient and related enzyme activity under different organic fertilizer proportions (OFP) could provide references for screening appropriate inoculant type, OFP, and fertilization period. Here, we set four OFP levels (mass ratio: 0%, 4%, 8%, 12%) and inoculated two phosphate-solubilizing bacteria (Bacillus megaterium, Pseudomonas fluorescens) and two N2-fixing bacteria (Azotobacter chroococcum, Azospirillum brasilence) in the subtropical yellow-brown barren soil. After a 60-day soil incubation under controlled conditions (28 ℃, darkness), we examined the impacts of single/mixed applications of beneficial bacteria on soil available nutrients and related enzyme activities at different OFP levels and different sampling times (3rd, 8th, 16th, 30th, 45th, 60th day). The results showed that soil available nutrient contents increased with the elevated OFP levels, and exhibited as 12%>8%>4%>0%. With the extension of culture time, soil nutrient contents in all treatments first increased and then decreased. Compared with the single application of organic fertilizer, combined application of organic fertilizer and bacterial inoculants resulted in higher and longer improvement of soil nutrient contents and enzyme activities. The effects of inoculants on soil nutrient properties varied across four OFP levels. When the OFP was low (0-4%), inoculation significantly increased soil available nutrient contents, with no the differences between inoculants at the initial stage. However, with the extension of the culture time and the elevation of OFP, phosphate-solubilizing bacteria (especially for B. megaterium) significantly increased available phosphorus content while N2-fixing bacteria (especially for A. brasilence) significantly increased available nitrogen content. The mixed inoculant with four strains showed phosphate-solubilizing effect on soil and performed better than the single application of phosphate-solubilizing bacteria, but without prominent effect on nitrogen fixation. Soil nutrient contents were positively correlated with enzyme activity, which was affected by both cultural time and carbon-nitrogen ratio. Bacterial inoculations could significantly increase nutrient contents in the short term, but the specific functions of beneficial bacteria on soil were highly dependent on organic carbon input and carbon-nitrogen ratio. Coupled application of inoculants and organic fertilizer at an appropriate OFP level (8%-12%) could increase and extend the soil-remediating effects, while the inoculation should be conducted with an interval of 45-60 days to ensure the survival rate and the consecutive effect on soil.

Hyperuricemia as a potential plausible risk factor for periodontitis.

Elevated blood uric acid (UA) levels have been positively associated with the severity of periodontitis. It thus brings out a hypothesis that hyperuricemia, a pathological elevation of blood UA, might be a risk factor for periodontitis. Namely, periodontitis individuals with Hu might acquire more severe periodontal destruction compared to those without Hu. To support the hypothesis, four aspects of evidences are proposed. First, hyperuricemia and periodontitis share many metabolic and inflammatory comorbidities such as metabolic syndrome, diabetes and cardiovascular diseases which are commonly related to elevated UA levels and gout. Second, observational and interventional studies have found altered UA levels in blood and saliva in periodontitis patients or after periodontal treatment, suggesting an epidemiological connection between hyperuricemia and periodontitis. Third, plausible immuno-metabolic mechanisms by which hyperuricemia might promote the progression of periodontitis are suggested, such as impaired immune response, oxidative stress, pathological bone remodeling and dysbiosis. The last, our empirical data exhibited elevated UA levels in gingival tissue in periodontitis mice compared to controls. If the hypothesis is true, given the high prevalence of the two conditions, hyperuricemia would be a significant risk factor increasing the global burden of periodontal diseases. Evidences on a directional correlation between hyperuricemia and periodontitis are sparse. Longitudinal and experimental studies would be necessary to determine the magnitude of periodontal risk, if any, exacerbated by hyperuricemia and the underlying mechanisms.

[Dendrobium officinale cliff epiphytic cultivation method].

To solve the issues of costly planting of facility cultivation method and inferior efficacy than wild herbs of Dendrobium officinale, the cliff epiphytic cultivation method was studied. To research the growth, agronomic traits, yield, polysaccharide and alcohol-soluble extract contents were measured on the D. officinale from different water regulation and cliff slope gradients treatments. The results showed that D. officinale epiphytic at 85 degrees-90 degrees cliff and sprayed water 1-2 h x d(-1) at the growing season can get better growth and obtain high yield, and the morphology has no different from wild cliff D. officinale, even in the environments without shade. The contents of polysaccharide and alcohol-soluble extract are closely related to the physiological ages, but significantly higher than the facility cultivation. It is possible that environmental stresses benefit the accumulation of polysaccharides, alcohol-soluble extract and other efficient ingredients.

Hybrid electron microscopy-FRET imaging localizes the dynamical C-terminus of Tfg2 in RNA polymerase II-TFIIF with nanometer precision.

TFIIF-a general transcription factor comprising two conserved subunits can associate with RNA polymerase II (RNAPII) tightly to regulate the synthesis of messenger RNA in eukaryotes. Herein, a hybrid method that combines electron microscopy (EM) and Förster resonance energy transfer (FRET) is described and used to localize the C-terminus of the second TFIIF subunit (Tfg2) in the architecture of RNAPII-TFIIF. In the first stage, a poly-histidine tag appended to the Tfg2 C-terminus was labeled with nickel-NTA nanogold and a seven-step single particle EM protocol was devised to obtain the region accessible by the nanogold in 3D, suggesting the Tfg2 C-terminus is proximal to the clamp of RNAPII. Next, the C-termini of the Rpb2 and the Rpb4 subunits of RNAPII, adjacent to the clamp, were selected for placing FRET satellites to enable the nano-positioning (NP) analysis, by which the localization precision was improved such that the Tfg2 C-terminus was found to dwell on the clamp ridge but could move to the clamp top during transcription. Because the tag receptive to the EM or FRET probes can be readily introduced to any protein subunit, this hybrid approach is generally applicable to complement cryo-EM study of many protein complexes to nanometer precision.