Microbial species pool-mediated diazotrophic community assembly in crop microbiomes during plant development

Plant-associated diazotrophs strongly relate to plant nitrogen (N) supply and growth. However, our knowledge of diazotrophic community assembly and microbial N metabolism in plant microbiomes is largely limited. Here we examined the assembly and temporal dynamics of diazotrophic communities across multiple compartments (soils, epiphytic and endophytic niches of root and leaf, and grain) of three cereal crops (maize, wheat, and barley) and identified the potential N-cycling pathways in phylloplane microbiomes. Our results demonstrated that the microbial species pool, influenced by site-specific environmental factors (e.g., edaphic factors), had a stronger effect than host selection (i.e., plant species and developmental stage) in shaping diazotrophic communities across the soil-plant continuum. Crop diazotrophic communities were dominated by a few taxa (~0.7% of diazotrophic phylotypes) which were mainly affiliated with Methylobacterium, Azospirillum, Bradyrhizobium, and Rhizobium. Furthermore, eight dominant taxa belonging to Azospirillum and Methylobacterium were identified as keystone diazotrophic taxa for three crops and were potentially associated with microbial network stability and crop yields. Metagenomic binning recovered 58 metagenome-assembled genomes (MAGs) from the phylloplane, and the majority of them were identified as novel species (37 MAGs) and harbored genes potentially related to multiple N metabolism processes (e.g., nitrate reduction). Notably, for the first time, a high-quality MAG harboring genes involved in the complete denitrification process was recovered in the phylloplane and showed high identity to Pseudomonas mendocina. Overall, these findings significantly expand our understanding of ecological drivers of crop diazotrophs and provide new insights into the potential microbial N metabolism in the phyllosphere.IMPORTANCEPlants harbor diverse nitrogen-fixing microorganisms (i.e., diazotrophic communities) in both belowground and aboveground tissues, which play a vital role in plant nitrogen supply and growth promotion. Understanding the assembly and temporal dynamics of crop diazotrophic communities is a prerequisite for harnessing them to promote plant growth. In this study, we show that the site-specific microbial species pool largely shapes the structure of diazotrophic communities in the leaves and roots of three cereal crops. We further identify keystone diazotrophic taxa in crop microbiomes and characterize potential microbial N metabolism pathways in the phyllosphere, which provides essential information for developing microbiome-based tools in future sustainable agricultural production.

Rare taxa maintain the stability of crop mycobiomes and ecosystem functions

Plants harbour highly diverse mycobiomes which sustain essential functions for host health and productivity. However, ecological processes that govern the plant-mycobiome assembly, interactions and their impact on ecosystem functions remain poorly known. Here we characterized the ecological role and community assembly of both abundant and rare fungal taxa along the soil-plant continuums (rhizosphere, phyllosphere and endosphere) in the maize-wheat/barley rotation system under different fertilization practices at two contrasting sites. Our results indicate that mycobiome assembly is shaped predominantly by compartment niche and host species rather than by environmental factors. Moreover, crop-associated fungal communities are dominated by few abundant taxa mainly belonging to Sordariomycetes and Dothideomycetes, while the majority of diversity within mycobiomes are represented by rare taxa. For plant compartments, the abundant sub-community is mainly determined by stochastic processes. In contrast, the rare sub-community is more sensitive to host selection and mainly governed by deterministic processes. Furthermore, our results demonstrate that rare taxa play an important role in fungal co-occurrence network and ecosystem functioning like crop yield and soil enzyme activities. These results significantly advance our understanding of crop mycobiome assembly and highlight the key role of rare taxa in sustaining the stability of crop mycobiomes and ecosystem functions.

[One case successfully rescued acute poisoning caused by misadministration of large amount of glufosinate]

Objective: To report a case of acute glufosinate-ammonium poisoning cause respiratory cardiac arrest and grass amine poisoning cases of successful rescue. Methods: The clinical data of a case of acute glufosinate-ammonium poisoning admitted to a third-class a hospital in April 2018 were analyzed and summarized. Results: The patient was poisoned by oral administration of a large amount of glufosinate-ammonium. Respiratory and cardiac arrest occurred during treatment and resuscitation was successful Later, the nervous system showed impaired function, The patients were treated with complete gastrointestinal cleansing, hemoperfusion, and the protection of important organs. Conclusion: For a large number of patients with oral glufosinate-ammonium poisoning, we should pay close attention to the damage of nervous system while taking active and conventional detoxification treatment.

Nitrate-induced and in situ electrochemical activation synthesis of oxygen deficiencies-rich nickel/nickel (oxy)hydroxide hybrid films for enhanced electrocatalytic water splitting

Hydrogen produced by electrochemical water splitting offers a hopeful and renewable solution for addressing the global energy crisis; however, development of highly efficient non-noble-metal electrocatalysts remains a big challenge. Herein, we report a facile strategy to fabricate oxygen deficiencies-rich nickel/nickel (oxy)hydroxide hybrid films as efficient electrocatalysts for water splitting by in situ oxygen evolution reaction (OER) activation. Under OER conditions, the originally deposited Ni films from the ethaline-based deep eutectic solvent (DES) undergo a structural rearrangement with a phase transformation in the oxidation state from Ni(ii) to Ni(iii) at the surface. The change is coupled with an increase in oxygen deficiencies and a pronounced defective precursor is induced by the addition of nitrate ions, providing structural disordering and boosting the intrinsic activity of the catalyst, which strongly enhances the water splitting performance.

Hugoniot equation of state of rock materials under shock compression

Two sets of shock compression tests (i.e. conventional and reverse impact) were conducted to determine the shock response of two rock materials using a plate impact facility. Embedded manganin stress gauges were used for the measurements of longitudinal stress and shock velocity. Photon Doppler velocimetry was used to capture the free surface velocity of the target. Experimental data were obtained on a fine-grained marble and a coarse-grained gabbro over a shock pressure range of approximately 1.5-12 GPa. Gabbro exhibited a linear Hugoniot equation of state (EOS) in the pressure-particle velocity (P-u_p) plane, while for marble a nonlinear response was observed. The EOS relations between shock velocity (U_S) and particle velocity (u_p) are linearly fitted as U_S = 2.62 + 3.319u_p and U_S = 5.4 85 + 1.038u_p for marble and gabbro, respectively.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

Effects of hypoxia on proliferation and osteogenic differentiation of periodontal ligament stem cells: an in vitro and in vivo study

Changes in oxygen concentration may influence various innate characteristics of stem cells. The effects of varying oxygen concentration on human periodontal ligament stem cells (HPDLSCs) has not been explored, particularly under hypoxia-related conditions. First, HPDLSCs were cultured from the periodontium of human teeth using the outgrowth method. STRO-1 and CD146 expression of HPDLSCs was investigated by flow cytometry. To detect the multilineage differentiation capacities of HPDLSCs, osteogenic-like and adipogenic-like states were induced in cells. Next, HPDLSCs (passage 3) were exposed to normal oxygen (21% O2) or hypoxia (2% O2) conditions for 7 days and cell proliferation was evaluated. After culture in osteogenic medium for 7 days, osteoblastic differentiation was evaluated by semi-quantitative reverse transcription-polymerase chain reaction analysis to detect 3 osteoblastic markers: core-binding factor a 1/runt-related transcription factor 2, osteocalcin, and osteopontin. In addition, each cell group was incubated with a hydroxyapatite/tricalcium phosphate carrier and transplanted subcutaneously into the back of immunocompromised mice to investigate transplantation differences in vivo. HPDLSCs were isolated, cultured, and successfully identified. After exposure of HPDLSCs to hypoxia for 7 days, the proliferation rate was increased and showed higher osteogenic differentiation potential compared to control cells. After 12 weeks of transplantation, hypoxia-treated HPDLSCs differentiated into osteoblast-like cells that formed bone-like structures. These results suggest that oxygen concentrations affect various aspects of HPDLSC physiology and that hypoxia enhances osteogenic differentiation both in vivo and in vitro. Oxygen concentration may be a critical parameter for HPDLSCs during expansion and differentiation.

Relationship between mucosal levels of interleukin 8 and toxinogenicity of Helicobacter pylori

AIM OF STUDY

To investigate if an association exists between in-vivo mucosal levels of IL-8 and bacterial expression of cytotoxin and cagA gene of H. pylori.

METHODS

Seventy-two dyspeptic patients referred for endoscopy were studied, including 36 patients with peptic ulcer (PU) and 36 with non-ulcer dyspepsia (NUD). Biopsies were taken for histology, H. pylori culture and measurement of IL-8 by ELISA. To test the ability of H. pylori to produce cytotoxin (VacA), broth culture supernatants were assayed on Vero cells and vacuolation measured. PCR was used to detect the cagA gene of H. pylori.

RESULTS

H. pylori was isolated in 52 of 72 patients studied. Among the 52 strains, 25 (49%) were VacA+ve/cagA+ve; 12 (23%) were VacA-ve/cagA-ve; the remaining 15 strains (28%) were either VacA+ve/cagA-ve or VacA-ve/cagA+ve. IL-8 levels (median (interquartile) pg/mg) in patients infected with VacA+ve (1.5 (0.64, 2.84)) or cagA+ve strains (1.25 (0.72, 2.34) were significantly higher than in those with VacA-ve (0.76 (0.4, 1.0)) or cagA-ve strains (0.5 (0.4, 1.5); p<0.05). The neutrophil infiltration score was also higher in patients infected with VacA+ve or cagA+ve strains than in those infected with VacA-ve or cagA-ve strains (p<0.05).

CONCLUSION

VacA+ve/cagA+ve strains were associated with an enhanced production of mucosal IL-8 in vivo and correlated with a stronger infiltration of neutrophils. Enhanced mucosal production of IL-8 and its role in neutrophil chemotaxis and activation could be important in H. pylori-induced gastroduodenal inflammation and in the development of peptic ulcer disease.

Reversal of the gastric effects of nicotine by nitric oxide donor treatment

Nicotine intensifies experimental gastric ulceration by reducing gastric mucosal blood flow (GMBF) and mucus. As both these parameters can be improved by nitric oxide (NO), we evaluated the impact of a NO donor in ethanol-induced gastric mucosal injury in rats administered nicotine. A nicotine solution or water was administered for 20 days to Sprague-Dawley rats. NO donor (isosorbide dinitrate) was given 60 and 10 min before preparation of ex vivo gastric chambers and exposure to ethanol. Chronic nicotine intake significantly reduced GMBF and gastric mucus content. Nicotine intensifies ethanol-induced gastric injury and short-term administration of NO donor failed to antagonize the ulcerogenic action from either nicotine or alcohol. In another study, rats drank nicotine solution for 20 days, after which the nicotine was withdrawn and replaced by water for 10 additional days. NO donor was provided during these last 10 days. The gastric effects of nicotine persisted for at least 10 days after nicotine was withdrawn but then these effects could be abolished by prolonged NO treatment. Nicotine reduces plasma nitrite level, but gastric mucosal MPO activity remained unchanged. Our data suggest that nicotine cessation plus a longer period of NO donor administration can completely abolish the gastric effects of nicotine.

Relationship between mucosal levels of Helicobacter pylori-specific IgA, interleukin-8 and gastric inflammation

Mucosal IgA is important in local immune defence. Helicobacter pylori induces a specific IgA response in antral mucosa, but its immunopathology is unknown. Interleukin-8 (IL-8) has been suggested to be important in H. pylori-induced inflammation. Current information on the relationship between H. pylori-induced IgA and mucosal inflammation is limited. To investigate possible associations between mucosal-specific IgA, the toxinogenicity of H. pylori, mucosal levels of IL-8 and gastric inflammation, 52 endoscoped patients were studied. These comprised 28 patients with peptic ulcer and 24 with non-ulcer dyspepsia. Of these patients, 38 had H. pylori infection: 28 with peptic ulcer and 10 with non-ulcer dyspepsia. Antral biopsies were taken for histology, H. pylori culture and measurement of mucosal levels of IL-8 (pg/mg) and specific IgA (A450x1000) by ELISA. Mucosal H. pylori IgA was detectable in 35 out of 38 patients with H. pylori infection, with a median (interquartile) level of 220 (147, 531) units. There was no significant difference in mucosal levels of the IgA antibodies between patients infected with cytotoxin-positive or cagA-positive strains of H. pylori and those with toxin-negative or cagA-negative strains. The IgA levels in those patients with severe neutrophil infiltration were lower than in those with mild or moderate infiltration (P<0.05). There was a weak inverse correlation between antral mucosal IgA and IL-8 in infected patients (r=-0.36; P=0.04). H. pylori infection induced a significant local mucosal IgA response in most infected patients. The level of IgA antibodies does not appear to be correlated with the toxinogenicity of H. pylori. However, patients with severe active inflammation appear to have decreased levels of IgA. An inverse correlation between mucosal IL-8 and IgA may suggest that IL-8-induced inflammation compromises the mucosal IgA defence and renders the mucosa susceptible to further damage.

Long-term efficacy of recombinant interferon alpha 2a in the treatment of chronic hepatitis C: a randomized prospective study comparing two dose schedules in Chinese patients

BACKGROUND/AIMS

This study is the first randomized prospective clinical trial of interferon in hepatitis to be conducted according to the guidelines of Good Clinical Practice (GCP) in China. The object of this study is to compare the long-term efficacy of a dose of 3MU of recombinant IFN alpha 2a (rIFN-alpha 2a) three times a week (t.i.w.) for 6 months with a starting dose of 6MU for 3 months and subsequent reduction to 3 MU t.i.w for a further 3 months.

METHODOLOGY

Sixty-eight serological and histologically proven chronic hepatitis C patients with elevated serum ALT were randomized into two groups. A total of 63 patients were studied with full course of treatment. Five patients were withdrawn from the trial, 2 due to personal reasons and 3 due to adverse drug reactions during treatment. Thirty patients received 6MU IFN-alpha 2a t.i.w. for 3 months followed by 3MU t.i.w. for another 3 months (group A). Thirty-three patients received 3MU IFN-alpha 2a t.i.w. for 6 months (group B).

RESULTS

The sex, age, baseline serum bilirubin, ALT and AST levels were matched in both groups. At the end of 6 months the complete and partial response rates in group A were 60.0% and 16.7%, respectively, and the clearance of serum HCV-RNA was 53.3%. In group B, the complete and partial response rates were 72.7% and 3.0%, respectively, and the clearance of HCV-RNA was 61.3%. These patients were followed up for 6, 12, and 18 months after stopping treatment. In group A, the rates of complete normalization of ALT and clearance of serum HCV-RNA at 24 months were 50.0% and 60.0%, respectively. In group B, the rates of normalization of ALT and clearance of HCV-RNA at 24 months were 54.4% and 41.9%, respectively. The efficacy between the two groups showed no statistically significant difference; the response rates of treatment were similar to the patients with HCV genotype 1b and 2a. Six patients (10.8% of the study population) developed neutralization antibodies to IFN-alpha 2a during treatment, 4 of them responded to the treatment. Adverse drug reactions (ADR) were common, but most of them were tolerable and the incidence of ADR was similar in both groups.

CONCLUSIONS

IFN-alpha 2a is effective in the treatment of Chinese patients with chronic hepatitis C. The sustained response rates and ADR among two dose schedule groups are similar.

Association of antral mucosal levels of interleukin 8 and reactive oxygen radicals in patients infected with Helicobacter pylori

1. Helicobacter pylori infection is characterized by an infiltration of neutrophils in the gastric mucosa. Neutrophil activation is an important source of reactive oxygen radicals, which cause tissue damage. Studies have shown that in Helicobacter pylori-infected patients there is increased mucosal production of interleukin 8. However, the role of interleukin 8 in the Helicobacter pylori-related inflammatory process and its relationship with reactive oxygen radicals remains to be clarified. The aims of this study were to investigate if there is any association between antral mucosal levels of interleukin 8 and reactive oxygen radicals and their relationship to gastric antral inflammation. 2. Fifty-two patients referred for endoscopy were recruited into the study. Gastric antral biopsies were taken for histology, culture and measurement of interleukin 8 and chemiluminescence (measuring reactive oxygen radicals). Interleukin 8 was measured by ELISA and the result expressed as pg/mg biopsy. Luminol-enhanced chemiluminescence was measured as mV min-1 mg-1 biopsy. Antral inflammation was assessed by a pathologist in a blinded fashion. 3. Antral mucosal levels of interleukin 8 and reactive oxygen radicals were significantly higher in Helicobacter pylori-colonized mucosa than in Helicobacter pylori-negative mucosa. After the eradication of Helicobacter pylori in patients with duodenal ulcer the median values (ranges) of interleukin 8 and reactive oxygen radicals fell from 1.21 (0.10-2.40) to 0.65 (0.00-1.60) and from 110.0 (10.0-959.0) to 14.5 (0.0-85.0) respectively. There was a positive correlation between interleukin 8 concentration and chemiluminescence response in the antral mucosa (r = 0.72). A higher interleukin 8 concentration was associated with greater neutrophil infiltration (r = 0.72) and mononuclear cell infiltration (r = 0.55); the magnitude of the chemiluminescence response was also positively associated with neutrophil (r = 0.77) and mononuclear cell infiltration (r = 0.59). 4. Interleukin 8 concentration is associated with an infiltration of neutrophils and mononuclear cells and is correlated with the production of reactive oxygen radicals in antral gastric mucosa infected with Helicobacter pylori. These findings suggest that interleukin 8 may be important in attracting and activating phagocytes to release reactive oxygen radicals, thereby causing mucosal damage.

Effect of omeprazole therapy on the survival of Helicobacter pylori, urease activity, and antral gastric histology in patients with duodenal ulcer

BACKGROUND

Helicobacter pylori is associated with chronic active gastritis and peptic ulceration (PU). Omeprazole is a proton pump inhibitor that is effective in healing PU and reducing gastritis. Previously it has been found that omeprazole has some bacteriostatic activity against H. pylori both in vitro and in vivo and in inhibiting urease activity in vitro. Our aim was to evaluate the effect of omeprazole on H. pylori colonization of the gastric mucosa, urease activity in vivo, and the presence of associated gastritis in patients with duodenal ulcer (DU).

MATERIALS AND METHODS

We studied 12 patients (7 men and 5 women, ages 22-68 yr) with Du larger than 5 mm in diameter with a positive CLOtest (Delta West Ltd., Australia). Omeprazole, 20 mg bid, was given for 8 weeks to each patient, patients were endoscoped at the end of this period to check for healing of DU, and repeat biopsies were obtained from the gastric antrum for histological analysis, CLOtest, and culture.

RESULTS

DU healed completely in all patients. Likewise in all patients there was significant reduction in the urease activity, from 22.1 +/- 4.17 to 1.58 +/- 0.92 units/ml (p < .001; 95% confidence interval of the difference between means, 32.7-14.1), and reduced H. pylori density, from 1,403.46 +/- 128.23 to 422.5 +/- 172.39 colony-forming units (CFU) per milligram of tissue biopsy (p < .001; 95% confidence interval of the difference between means, 1,486.1-590.5). The numbers of H. pylori were reduced on the gastric mucosa after omeprazole therapy and disappeared in six patients, a result that correlated with a negative CLOtest reading after 24 hours.

CONCLUSION

Omeprazole, 20 mg bid, is capable of reducing H. pylori numbers and urease activity in vivo. There was no significant reduction in the severity of antral gastritis in DU patients studied.

Association of cytotoxin production and neutrophil activation by strains of Helicobacter pylori isolated from patients with peptic ulceration and chronic gastritis

BACKGROUND

Helicobacter pylori is associated with neutrophil infiltration within the gastroduodenal mucosa. Neutrophil activation provides a major source of oxygen free radicals, which have been implicated in the pathogenesis of peptic ulceration.

AIM

To investigate if cytotoxin producing strains of H pylori are associated with the generation of oxidative burst in polymorphonuclear neutrophils (PMNs).

PATIENTS

76 patients undergoing endoscopy of whom 45 had peptic ulcer and 31 chronic gastritis only were studied.

METHODS

Strains of H pylori were cultured in Brucella broth. After 48 hours, bacteria were harvested by centrifugation and a bacterial suspension prepared as a stimulus for PMN oxidative burst using chemiluminescence. PMNs were prepared from health blood donors. To test the ability of strains to produce cytotoxin, culture supernatants of each were concentrated by polyethylene glycol and tested on cultured Vero cells for intracellular vacuolation.

RESULTS

30 of 45 (66.7%) peptic ulcer patients induced cell vacuolation versus nine of 31 (29%) strains from patients with chronic gastritis only (p < 0.01). Cytotoxin positive strains of H pylori regardless of the presence or absence of peptic ulcer displayed an increased induction of respiratory burst in PMNs compared with toxin negative strains from patients with chronic gastritis only (p < 0.05). Among the toxin negative strains, those from patients with peptic ulcer did not show a significant increase of the oxidative burst than those from patients without peptic ulcer (NS).

CONCLUSION

Toxinogenicity of strains of H pylori seems to be correlated with neutrophil respiratory burst and peptic ulceration. The ability of some strains of H pylori to produce cytotoxin and to induce the oxidative burst in neutrophils may be important in the pathogenesis of peptic ulcer disease.

Effects of exogenous gamma-aminobutyric acid on experimental arrhythmias

The effects of exogenous gamma-aminobutyric acid (GABA) 10 mg.kg-1 iv in preventing arrhythmias induced by drugs and ischemia were studied in mice, rats, and guinea pigs. It was found that the threshold dose of aconitine inducing arrhythmia in mice and the recovery rate to normal sinus rhythm increased significantly, ED50 of GABA was 5.4-5.8 mg.kg-1. The duration of ventricular tachycardia (VT) induced by aconitine in rats was shortened (P < 0.01). The incidence and the mortality of ventricular fibrillation (VF) in GABA group were decreased to 0/10 vs 6/10 and 5/10 in control, respectively (P < 0.05). The doses of ouabain to induce ectopic beats (EB), VT, VF, and cardiac arrest (CA) in guinea pigs were increased (P < 0.01). The incidence of VF induced by coronary artery ligation in rats was decreased to 0/5 in GABA group vs 4/5 in control group (P < 0.01). The total amount of EB, total time of VT, and VF were 66%, 41%, and 0% of the control group, respectively. The anti-arrhythmic effects of GABA were dose-dependent and as potent as procainamide (10 or 5 mg.kg-1, iv). The results suggest GABA (10 mg.kg-1, iv) may be useful for the prevention of VT and VF.

Vaginal radical hysterectomy for uterine cervical cancer

The incidence of uterine cervical carcinoma, though decreasing in many cities of China, dose not show any diminution in the rural areas where it appears to be high in some regions. Therefore, radical hysterectomy is particularly important for the patients with cervical adenocarcinoma and squamous adenocarcinoma which are insensitive to chemotherapy and radiotherapy. The operation is effective in the treatment of early cervical carcinoma and even late carcinoma when the procedure is combined with extraperitoneal radical lymphadenectomy, radiotherapy and chemotherapy reinforced by the traditional Chinese medicine. This operation gets rid of technical difficulties in manipulating the deep pelvic cavities of obese patients, and is suitable for those patients with general weakness, heart and renal diseases, hypertension, severe tuberculosis complicated by the poor tolerance of the abdomen or fear to transabdominal procedures. The detailed procedures of the operation and its results are described.

[Enzyme-linked immunosorbent assay for the serodiagnosis of Campylobacter pylori infection]

Antibody activities to campylobacter pylori in serum were estimated by an enzyme-linked immunosorbent assay (ELISA) to crude antigens, prepared by sonication of whole organisms obtained from bacterial culture in 100 patients with chronic gastritis. Significantly raised serum IgG antibody activities to C. pylori was found in colonised patients with gastritis, especially in patients with active gastritis. High activities were also found beyond the age of 30. In 6 patients cleared of C. pylori with furazolidone and/or colloidal bismuth subcitrate (De-NoL), serial testing has shown a fall in activity to normal level by 1/2 year in 4 patients. The specificity and sensitivity of the sero-diagnostic assay was 85.3% and 97% respectively. The positive and negative predictive values were 92.8% and 93.5% respectively. The results indicate that such a serodiagnostic assay could be used to screen patients with C. pylori colonisation in epidemiological surveys.