A novel antimicrobial peptide S24 combats serious wound infections caused by Pseudomonas aeruginosa and Acinetobacter baumannii.

OBJECTIVES: Pseudomonas aeruginosa and Acinetobacter baumannii are ranked as top-priority organisms by WHO. Antimicrobial peptides (AMPs) are promising antimicrobial agents that are highly effective against serious bacterial infections. METHODS: In our previous study, a series of α-helical AMPs were screened using a novel multiple-descriptor strategy. The current research suggested that S24 exhibited strong antimicrobial activity against major pathogenic bacteria, and displayed minimal haemolysis, good serum stability and maintained salt resistance. RESULTS: We found that S24 exerted an antimicrobial effect by destroying outer membrane permeability and producing a strong binding effect on bacterial genomic DNA that inhibits genomic DNA migration. Furthermore, S24 exerted a strong ability to promote healing in wound infected by P. aeruginosa, A. baumannii and mixed strains in a mouse model. CONCLUSIONS: Overall, S24 showed good stability under physiological conditions and excellent antimicrobial activity, suggesting it may be a potential candidate for the development of serious bacterial infection treatment.

Associations of per- and polyfluoroalkyl substances (PFAS) and their mixture with risk of rheumatoid arthritis in the U.S. adult population.

BACKGROUND: Per- and polyfluoroalkyl substances (PFAS) are known environmental contaminants with immunosuppressive properties. Their connection to rheumatoid arthritis (RA), a condition influenced by the immune system, is not well studied. This research explores the association between PFAS exposure and RA prevalence. METHODS: This research utilized data from the NHANES, encompassing a sample of 10,496 adults from the 2003-2018 cycles, focusing on serum levels of several PFAS. The presence of RA was determined based on self-reports. This study used multivariable logistic regression to assess the relationship between individual PFAS and RA risk, adjusting for covariates to calculate odds ratios (ORs). The combined effects of PFAS mixtures were evaluated using BKMR, WQS regression, and quantile g-computation. Additionally, sex-specific associations were explored through stratified analysis. RESULTS: Higher serum PFOA (OR = 0.88, 95% CI: 0.79, 0.98), PFHxS (OR = 0.91, 95% CI: 0.83, 1.00), PFNA (OR = 0.87, 95% CI: 0.77, 0.98), and PFDA (OR = 0.89, 95% CI: 0.81, 0.99) concentration was related to lower odds of RA. Sex-specific analysis in single chemical models indicated the significant inverse associations were only evident in females. BKMR did not show an obvious pattern of RA estimates across PFAS mixture. The outcomes of sex-stratified quantile g-computation demonstrated that an increase in PFAS mixture was associated with a decreased odds of RA in females (OR: 0.76, 95% CI: 0.62, 0.92). We identified a significant interaction term of the WQS*sex in the 100 repeated hold out WQS analysis. Notably, a higher concentration of the PFAS mixture was significantly associated with reduced odds of RA in females (mean OR = 0.93, 95% CI: 0.88, 0.98). CONCLUSIONS: This study indicates potential sex-specific associations of exposure to various individual PFAS and their mixtures with RA. Notably, the observed inverse relationships were statistically significant in females but not in males. These findings contribute to the growing body of evidence indicating that PFAS may have immunosuppressive effects.

Exploration of the Dynamic Variations of the Characteristic Constituents and the Degradation Products of Catalpol during the Process of Radix Rehmanniae.

Radix Rehmanniae (RR), a famous traditional Chinese medicine (TCM) widely employed in nourishing Yin and invigorating the kidney, has three common processing forms in clinical practice, including fresh Radix Rehmanniae (FRR), raw Radix Rehmanniae (RRR), and processed Radix Rehmanniae (PRR). However, until now, there has been less exploration of the dynamic variations in the characteristic constituents and degradation products of catalpol as a representative iridoid glycoside with the highest content in RR during the process from FRR to PRR. In this study, an ultra-performance liquid chromatography coupled with photodiode array detector (UPLC-PDA) method was successfully established for the simultaneous determination of ten characteristic components to explore their dynamic variations in different processed products of RR. Among them, iridoid glycosides, especially catalpol, exhibited a sharp decrease from RRR to PRR. Then, three degradation products of catalpol were detected under simulated processing conditions (100 °C, pH 4.8 acetate buffer solution), which were isolated and identified as jiofuraldehyde, cataldehyde, and norviburtinal, respectively. Cataldehyde was first reported as a new compound. Moreover, the specificity of norviburtinal in self-made PRR samples was discovered and validated, which was further confirmed by testing in commercially available PRR samples. In conclusion, our study revealed the decrease in iridoid glycosides and the production of new degradation substances during the process from FRR to PRR, which is critical for unveiling the processing mechanism of RR.

Development and Validation of a Patient Discharge Readiness Scale for Daytime Cataract Surgery (DRS-CAT).

PURPOSE: To ensure the safety of patients discharged from the hospital, a nurse-assessed scale for outpatient cataract surgery patients was constructed to provide a special tool for cataract patients' discharge readiness evaluation. DESIGN: This is a methodological study. METHODS: The development of the tool was completed between 2021 and 2022. Based on the literature review and qualitative interviews, the initial entry pool of the discharge readiness scale was established. After consultation with Delphi experts, the preliminary scale was tested by 312 participants to screen items and test reliability and validity. The analysis included internal consistency, content validity, and construct validity. The Strengthening the Reporting of Observation studies in Epidemiology (STROBE) checklist was used as the reporting guideline for this study. FINDINGS: The final Discharge Readiness Scale for Cataract surgery consists of 21 items in five dimensions: cognition of discharge readiness, personal status, mastery of health education knowledge, coping capacity, and social support. Five common factors were extracted from the exploratory factor analysis, and they explained 70.12% of the total variance. All of the indexes of the confirmatory factor analysis were within the theoretical allowable range. The Cronbach's α of the total scale was 0.903, and the scale-level content validity index/average variance extracted was 0.99. CONCLUSIONS: The Discharge Readiness Scale for Cataract surgery, evaluated by nurses, has good reliability and validity and can be used to determine the discharge readiness of cataract patients undergoing day surgery.

Metal-Free Highly Regioselective 1,4-Sulfonyliodination of 1,3-Enynes.

Herein, a novel, practical, and green synthetic method using readily available 1,3-enynes with sulfonyl hydrazides and I2 through tert-butyl hydroperoxide (TBHP)-mediated 1,4-sulfonyliodination has been developed for synthesizing various tetrasubstituted allenyl iodides under metal-free conditions. Notably, the proposed method exhibits a broad substrate scope, operational simplicity, tolerance to air, high functional-group tolerance, satisfactory yields, and excellent regioselectivity as well as involves the use of cost-effective reagents such as green oxidants.

The effectiveness of WeChat couple-based psychosocial support for gynaecological cancer: A randomised controlled trial.

OBJECTIVE: This study aimed to evaluate the effectiveness of an 8-week electronic couple-based psychosocial support platform (WeChat) for gynaecological cancer. DESIGN: Randomised controlled trial. SETTING: Oncology hospital in Shaanxi Province, China. PARTICIPANTS: A total of 98 dyads of women with gynaecological cancer and their intimate male partners were included. METHODS: Couple dyads were randomly allocated to either the WeChat couple-based psychosocial support or to a control group receiving eight WeChat articles on general education content related to diet and exercise. MAIN OUTCOME MEASURES: The primary outcome was sexual function assessed with the Female Sexual Function Index. The secondary outcomes of relationship satisfaction and quality of life were assessed with the Chinese version of Revised Dyadic Adjustment Scale, Functional Assessment of Cancer Therapy-General and The World Health Organization Quality of Life BREF. These outcomes were assessed before randomisation, and immediately and 3 months after the intervention. RESULTS: The study showed that the sexual function of women participants in the intervention group did not reach a significant level compared with the control group. Relationship satisfaction in the intervention programme improved significantly (adjusted mean difference 4.7, 95% confidence interval [CI] 2.0-7.4; p = 0.001) and quality of life (QoL 6.9, 95% CI 0.5-13.3; p = 0.035) 3 months after the intervention in women with gynaecological cancer. The intervention programme also showed significant positive effects on optimising relationship satisfaction (adjuste mean difference 3.0, 95% CI 0.3-5.7; p = 0.027) of male partners. CONCLUSIONS: The results provided additional knowledge and an evidence base for the application of the support programme to improve relationship satisfaction and QoL among couples living with gynaecological cancer.

Development and evaluation of machine learning models and nomogram for the prediction of severe acute pancreatitis.

BACKGROUND AND AIM: Severe acute pancreatitis (SAP) in patients progresses rapidly and can cause multiple organ failures associated with high mortality. We aimed to train a machine learning (ML) model and establish a nomogram that could identify SAP, early in the course of acute pancreatitis (AP). METHODS: In this retrospective study, 631 patients with AP were enrolled in the training cohort. For predicting SAP early, five supervised ML models were employed, such as random forest (RF), K-nearest neighbors (KNN), and naive Bayes (NB), which were evaluated by accuracy (ACC) and the areas under the receiver operating characteristic curve (AUC). The nomogram was established, and the predictive ability was assessed by the calibration curve and AUC. They were externally validated by an independent cohort of 109 patients with AP. RESULTS: In the training cohort, the AUC of RF, KNN, and NB models were 0.969, 0.954, and 0.951, respectively, while the AUC of the Bedside Index for Severity in Acute Pancreatitis (BISAP), Ranson and Glasgow scores were only 0.796, 0.847, and 0.837, respectively. In the validation cohort, the RF model also showed the highest AUC, which was 0.961. The AUC for the nomogram was 0.888 and 0.955 in the training and validation cohort, respectively. CONCLUSIONS: Our findings suggested that the RF model exhibited the best predictive performance, and the nomogram provided a visual scoring model for clinical practice. Our models may serve as practical tools for facilitating personalized treatment options and improving clinical outcomes through pre-treatment stratification of patients with AP.

Exploring the sources of cervical cancer screening self-efficacy among rural females: A qualitative study.

AIM: Evidence showed self-efficacy was relevant to rural females' cervical cancer screening behaviour. However, little is known about sources of self-efficacy in cervical cancer screening among rural females. This study aimed to explore sources of self-efficacy in cervical cancer screening among rural females. DESIGN: A qualitative descriptive study was conducted. Both users and providers of cervical cancer screening services in rural areas of China were recruited through maximum variation sampling. METHODS: Individual semi-structured interviews through telephone calls were conducted. Data were analysed via six main stages of the framework method, with the social cognitive theory as a reference. RESULTS: Four main sources were identified, including personal screening experience, hearing about other women's screening experiences, professional health education and consultation, and emotional status. Personal screening experience included enactive mastery of completing the screening behaviour and cognitive mastery of internalisation of the screening. Only the experience of completing cervical cancer screening behaviour was not strong enough to improve self-efficacy. Cognitive mastery showed more critical influence. CONCLUSION: These four sources of rural females' cervical cancer screening self-efficacy matched with the major sources of self-efficacy of the social cognitive theory. Cognition was critical to influencing the screening self-efficacy. Intervention strategies aimed at enhancing rural females' cervical cancer screening self-efficacy can be developed from these four major sources. PUBLIC CONTRIBUTION: A registered nurse with rich experience in cervical cancer-related research and qualitative study was the interviewer of this study. Rural females and cervical cancer screening services providers (healthcare professionals and village staff) were recruited as interviewees. The interview guides were developed by the research team and evaluated by an expert panel including two nurse leaders of gynaecological cancer, one doctor specialised in cervical cancer, and one medical director in a local rural hospital.

The Use of Antimicrobial Drug in Patients During the COVID-19 Pandemic: A Meta-Analysis.

Objective: To analyze the use of antimicrobial drugs in patients during the COVID-19 pandemic. Methods: We searched for literature about antimicrobial treatment in COVID-19 patients through the Cochrane Library, Embase, PubMed, the Chinese biomedical literature database, CNKI, the Chinese journal full-text database, Wanfang, and Vipu. The quality evaluation of the literature was performed by Jadad's quality score. Results: A total of three articles reported on ivermectin treatment in patients with COVID-19, and the Meta-analysis showed no clinical and statistical heterogeneity among the studies (I2 = 15%, P = .31), a fixed effect model was used to incorporate effect sizes. The clinical effect of the observed group was not different from the control group (P = .16). None of the three ivermectin articles with clinical effect as the effect indicator showed a significant difference (P > .05), suggesting no publication bias. A total of four publications reported the treatment with azithromycin in patients with COVID-19, and the Meta-analysis showed no clinical and statistical heterogeneity between the studies (I2 = 0%, P = .88), using a fixed-effect model to incorporate the effect sizes. The clinical effect of the observed group was not different from the control group (P = .57). None of the four azithromycin articles with a clinical effect as the effect index was statistically significant (P > .05), suggesting no publication bias. Conclusion: During the COVID-19 pandemic, the patient's use of antibiotics does not significantly improve clinical efficacy, so antibiotic use is recommended only for patients with complicated bacterial infections.

The experience of diabetic retinopathy patients during hospital-to-home full-cycle care: A qualitative study.

BACKGROUND: Diabetic retinopathy (DR) is one of the major blinding eye diseases worldwide. Psychological, emotional and social problems of DR patients are prominent. The aim of this study is to explore the experiences of patients with different phases of DR from hospital to home based on the "Timing It Right" framework, and to provide a reference for formulating corresponding intervention strategies. METHODS: The phenomenological method and semi-structured interviews were used in this study. A total of 40 patients with DR in different phases were recruited from a tertiary eye hospital between April and August 2022. Colaizzi's analysis method was used to analyse the interview data. RESULTS: Based on the "Timing It Right" framework, different experiences in five phases of DR before and after Pars Plana Vitrectomy (PPV) were extracted. The patients experienced complicated emotional reactions and inadequate coping skills during the pre-surgery phase, increased uncertainty during the post-surgery phase, insufficient confidence and the decision to change during the discharge preparation phase, eagerness for professional support and moving forward in exploration during the discharge adjustment phase, and courageous acceptance and positive integration during the discharge adaptation phase. CONCLUSION: The experiences of DR patients with vitrectomy in different phases of disease are ever-changing, and medical staff should provide personalized support and guidance to help DR patients get through the hard times smoothly and enhance the quality of hospital-family holistic care.

Practice of the training program for ophthalmic specialist nurses in Zhejiang Province of China.

AIMS: To explore the effects of training programs for ophthalmic specialist nurses in Zhejiang Province of China. METHODS: The training program included one month of theoretical training and three months of practical clinical training. The Two-Tutor system was used in training. The training contents were mainly set up around four modules: specialty knowledge and clinical skills, management, clinical teaching, and nursing research. We used theoretical examination, clinical practice assessment and trainee evaluation to assess the effectiveness of the training program. Before and after the training, the trainees' core competence was assessed by a homemade questionnaire. RESULTS: In total, 48 trainees from 7 provinces (municipalities) in China participated in the training program. All trainees passed theoretical and clinical practice examinations and trainee evaluations. Their core competencies were significantly improved after training (p < 0.05). CONCLUSION: This training program for ophthalmic specialist nurses is scientific and effective in improving nurses' ability to provide ophthalmic specialist nursing care.

Boron-Doped and Ketonic Carbonyl Group-Enriched Graphdiyne as a Dual-Site Carbon Nanozyme with Enhanced Peroxidase-Like Activity.

We demonstrate the preparation of a dual-site carbon nanozyme, boron-doped and ketonic carbonyl (-C=O) group-enriched graphdiyne (B-GDY), with an enhanced peroxidase-like activity. Taking advantage of acidic oxidation treatment, GDY oxide (GDYO) with abundant surface oxygen-containing groups is obtained from pristine bulk GDY. Upon further thermal annealing of GDYO with H3BO3 under an inert atmosphere, B is introduced into GDY, while the loading of -C=O groups is increased onto B-GDY. We discover that boron-doped and ketonic carbonyl group-enriched graphdiyne as a dual-site carbon nanozyme endows it with an enhanced peroxidase-like activity, which is nearly 4.2-fold higher than that of GDY without B atoms and 6.6-fold higher than that of GDYO without B atoms and with low loading of -C=O groups. The high peroxidase-like activity of B-GDY is ascribed to the dual active sites (-C=O group and B atom) within it, which facilitates the adsorption and decomposition of H2O2 into hydroxyl radicals revealed by experimental and theoretical studies. Moreover, B-GDY is successfully employed to develop a colorimetric method for the detection of glucose with good sensitivity and selectivity. This work probes into the intrinsic peroxidase activity and structure-reactivity correlation, creating effective strategies for the preparation of GDY-based nanozymes.

Serratia marcescens PLR enhances lateral root formation through supplying PLR-derived auxin and enhancing auxin biosynthesis in Arabidopsis.

Plant growth promoting rhizobacteria (PGPR) refer to bacteria that colonize the rhizosphere and contribute to plant growth or stress tolerance. To further understand the molecular mechanism by which PGPR exhibit symbiosis with plants, we performed a high-throughput single colony screening from the rhizosphere, and uncovered a bacterium (named promoting lateral root, PLR) that significantly promotes Arabidopsis lateral root formation. By 16S rDNA sequencing, PLR was identified as a novel sub-species of Serratia marcescens. RNA-seq analysis of Arabidopsis integrated with phenotypic verification of auxin signalling mutants demonstrated that the promoting effect of PLR on lateral root formation is dependent on auxin signalling. Furthermore, PLR enhanced tryptophan-dependent indole-3-acetic acid (IAA) synthesis by inducing multiple auxin biosynthesis genes in Arabidopsis. Genome-wide sequencing of PLR integrated with the identification of IAA and its precursors in PLR exudates showed that tryptophan treatment significantly enhanced the ability of PLR to produce IAA and its precursors. Interestingly, PLR induced the expression of multiple nutrient (N, P, K, S) transporter genes in Arabidopsis in an auxin-independent manner. This study provides evidence of how PLR enhances plant growth through fine-tuning auxin biosynthesis and signalling in Arabidopsis, implying a potential application of PLR in crop yield improvement through accelerating root development.

Effects of music intervention on anxiety, depression, and quality of life of cancer patients receiving chemotherapy: a systematic review and meta-analysis.

BACKGROUND: Music may be a safe and effective coping strategy for psychological management. The objectives of this review were to identify the effects of music interventions on anxiety, depression, and quality of life (QoL) among cancer patients receiving chemotherapy. METHODS: Fourteen databases were searched from the inception date to December 2020 to identify eligible randomized controlled trials (RCTs). Gray literature was also examined. The protocol of this systematic review was registered with PROSPERO (registration number: CRD42021223845). Two reviewers independently assessed eligibility, extracted data, and evaluated methodological quality. Meta-analysis was done. Subgroup analysis was conducted for intervention types, the person selecting music, music delivery method, timing, and session duration. RESULTS: Nine RCTs were identified, among which six were eligible for the meta-analysis. All studies were at a high risk of bias, and the overall quality of evidence was low to very low. The pooled results reveal that music intervention could reduce anxiety (SMD: - 0.29, 95% CI - 0.50 to - 0.08) and improve QoL (SMD: 0.42, 95% CI 0.02 to 0.82). However, it fails to affect depression (p = 0.79). The findings demonstrate no significant difference between patient-selected music and researcher-selected music, recorded music, and live music, while a length of 15-20 min/session and offering immediately before chemotherapy are more effective on anxiety than that of 30-45 min and delivering during chemotherapy. CONCLUSIONS: Music intervention may be a beneficial tool for anxiety reduction and QoL among cancer patients receiving chemotherapy. More high-quality RCTs are needed to ascertain the true impact of those outcomes.

Self-Terminated Electroless Deposition of Surfactant-Free and Monodispersed Pt Nanoparticles on Carbon Fiber Microelectrodes for Sensitive Detection of H2O2 Released from Living Cells.

We report a self-terminated electroless deposition method to prepare surfactant-free and monodispersed Pt nanoparticle (NP)-modified carbon fiber microelectrodes (Pt NP/CFEs) for electrochemical detection of hydrogen peroxide (H2O2) released from living cells. The surfactant-free and monodispersed Pt NPs with a uniform size of 65 nm are spontaneously deposited on a CFE surface by immersing an exposed carbon fiber (CF) of CFE in the PtCl42- solution, in which an exposed CF can be used as the reducing agent and stabilizer. A self-terminated electroless deposition method is demonstrated, in which the density and size of Pt NPs on a CFE surface do not increase when the reaction time increases from 20 to 60 min. The self-terminated electroless deposition process not only can effectively avoid any manual electrode modification and thus largely minimize person-to-person and electrode-to-electrode deviations but also can avoid the use of any extra reductant or surfactant in the fabrication process. Therefore, Pt NPs/CFEs, with good reproducibility and sensitivity, not only exhibit high electrocatalytic activity toward the oxidation of H2O2 but also maintain the spatial resolution of CFEs. Moreover, Pt NPs/CFEs can detect H2O2 with a wide linear range of 0.5-80 µM and a low detection limit of 0.17 µM and then can be successfully applied in the monitoring of H2O2 released from RAW 264.7 cells. The self-terminated electroless deposition method can also be extended to selectively prepare other metal NP-modified CFEs, such as Au NPs/CFEs or Ag NPs/CFEs, by choosing the metal ions with higher reduction potential as precursors. This work provides a simple, straightforward, and general method for the preparation of small, surfactant-free, and monodispersed metal NP-modified CFEs with high sensitivity, reproducibility, and spatial resolution.

CO2 is a key constituent of the plant growth-promoting volatiles generated by bacteria in a sealed system.

KEY MESSAGE: Plant growth is greatly inhibited in tightly sealed Petri dishes for lack of CO2. Bacteria which co-cultured with plant can produce CO2 to promote plant growth in sealed systems. Bacteria produce a wide variety of volatiles, some of which can support and others can damage plant growth. It is a controversial issue whether CO2 or other bacterial volatile compounds promote plant growth in sealed systems. CO2 is critical for photosynthesis. Here, we show that CO2 is a key constituent of the plant growth-promoting volatiles generated by bacteria in a sealed system. We revealed that the growth of Arabidopsis seedlings in an airtight container was retarded due to insufficient supply of the CO2. When either CO2 was introduced into the container, or the seedlings were co-cultured along with certain bacterial species, the plants' growth was restored. CONCLUSION: The benefit of co-culturing was largely due to the CO2 generated by respiration of the bacteria.

Reducing the nicotine content of tobacco by grafting with eggplant.

BACKGROUND: Nicotine is a stimulant and potent parasympathomimetic alkaloid that accounts for 96-98% of alkaloid content. A reduction in the amount of nicotine in cigarettes to achieve a non-addictive level is necessary. We investigated whether replacing tobacco root with eggplant by grafting can restrict nicotine biosynthesis and produce tobacco leaves with ultra-low nicotine content, and analyzed the gene expression differences induced by eggplant grafting. RESULTS: The nicotine levels of grafted tobacco leaves decreased dramatically. The contents of nornicotine, anabasine, NNN, NNK, NAT, total TSNAs and the nicotine of mainstream cigarette smoke decreased, and the contents of amino acids and the precursors of alkaloids increased in grafted tobacco. Eggplant grafting resulted in the differential expression of 440 genes. LOC107774053 had higher degrees in two PPI networks, which were regulated by LOC107802531 and LOC107828746 in the TF-target network. CONCLUSIONS: Replacing tobacco root with eggplant by grafting can restrict nicotine biosynthesis and produce tobacco leaves with ultra-low or zero nicotine content. The differential expression of LOC107774053 may be associated with eggplant grafting.

Biosynthesis Gene Cluster and Oxazole Ring Formation Enzyme for Inthomycins in Streptomyces sp. Strain SYP-A7193.

Inthomycins belong to a growing family of oxazole-containing polyketides and exhibit a broad spectrum of anti-oomycete and herbicidal activities. In this study, we purified inthomycins A and B from the metabolites of Streptomyces sp. strain SYP-A7193 and determined their chemical structures. Genome sequencing, comparative genomic analysis, and gene disruption of Streptomyces sp. SYP-A7193 showed that the inthomycin biosynthetic gene cluster (itm) belonged to the hybrid polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) system. Functional domain comparison and disruption/complementation experiments of itm12 resulted in the complete loss of inthomycins A and B and the subsequent restoration of their production, confirming that itm12 encodes a discrete acyltransferase (AT), and hence, itm was considered to belong to the trans-AT type I PKS system. Moreover, the disruption/complementation experiments of itm15 also resulted in the loss and restoration of inthomycin A and B formation. Further gene cloning, expression, purification, and activity verification of itm15 revealed that Itm15 is a cyclodehydratase that catalyzes a straight-chain dehydration reaction to form an oxazole ring for the biosynthesis of inthomycins A and B. Thus, we discovered a novel enzyme that catalyzes oxazole ring formation and elucidated the complete biosynthetic pathway of inthomycins.IMPORTANCEStreptomyces species produce numerous secondary metabolites with diverse structures and pharmacological activities that are beneficial for human health and have several applications in agriculture. In this study, hybrid nonribosomal peptide synthetase/polyketide synthase metabolites inthomycins A and B were isolated from after fermenting Streptomyces sp. SYP-A7193. Genome sequencing, gene disruption, gene complementation, heterologous expression, and activity assay revealed that the biosynthesis gene assembly line of inthomycins A and B was a 95.3-kb trans-AT type I PKS system in the strain SYP-A7193. More importantly, Itm15, a cyclodehydratase, was identified to be an oxazole ring formation enzyme required for the biosynthesis of inthomycins A and B; it is significant to discover this catalyzation reaction in the PKS/NRPS system in the field of microbiology. Our findings could provide further insights into the diversity of trans-AT type I PKS systems and the mechanism of oxazole cyclization involved in the biosynthesis of natural products.

Insights into Streptomyces spp. isolated from the rhizospheric soil of Panax notoginseng: isolation, antimicrobial activity and biosynthetic potential for polyketides and non-ribosomal peptides.

BACKGROUND: Streptomycetes from the rhizospheric soils are a rich resource of novel secondary metabolites with various biological activities. However, there is still little information related to the isolation, antimicrobial activity and biosynthetic potential for polyketide and non-ribosomal peptide discovery associated with the rhizospheric streptomycetes of Panax notoginseng. Thus, the aims of the present study are to (i) identify culturable streptomycetes from the rhizospheric soil of P. notoginseng by 16S rRNA gene, (ii) evaluate the antimicrobial activities of isolates and analyze the biosynthetic gene encoding polyketide synthases (PKSs) and nonribosomal peptide synthetases (NRPSs) of isolates, (iii) detect the bioactive secondary metabolites from selected streptomycetes, (iv) study the influence of the selected isolate on the growth of P. notoginseng in the continuous cropping field. This study would provide a preliminary basis for the further discovery of the secondary metabolites from streptomycetes isolated from the rhizospheric soil of P. notoginseng and their further utilization for biocontrol of plants. RESULTS: A total of 42 strains representing 42 species of the genus Streptomyces were isolated from 12 rhizospheric soil samples in the cultivation field of P. notoginseng and were analyzed by 16S rRNA gene sequencing. Overall, 40 crude cell extracts out of 42 under two culture conditions showed antibacterial and antifungal activities. Also, the presence of biosynthesis genes encoding type I and II polyketide synthase (PKS I and PKS II) and nonribosomal peptide synthetases (NRPSs) in 42 strains were established. Based on characteristic chemical profiles screening by High Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD), the secondary metabolite profiles of strain SYP-A7257 were evaluated by High Performance Liquid Chromatography-High Resolution Mass Spectrometry (HPLC-HRMS). Finally, four compounds actinomycin X2 (F1), fungichromin (F2), thailandin B (F7) and antifungalmycin (F8) were isolated from strain SYP-A7257 by using chromatography techniques, UV, HR-ESI-MS and NMR, and their antimicrobial activities against the test bacteria and fungus were also evaluated. In the farm experiments, Streptomyces sp. SYP-A7257 showed healthy growth promotion and survival rate improvement of P. notoginseng in the continuous cropping field. CONCLUSIONS: We demonstrated the P. notoginseng rhizospheric soil-derived Streptomyces spp. distribution and diversity with respect to their metabolic potential for polyketides and non-ribosomal peptides, as well as the presence of biosynthesis genes PKS I, PKS II and NRPSs. Our results showed that cultivatable Streptomyces isolates from the rhizospheric soils of P. notoginseng have the ability to produce bioactive secondary metabolites. The farm experiments suggested that the rhizospheric soil Streptomyces sp. SYP-A7257 may be a potential biological control agent for healthy growth promotion and survival rate improvement of P. notoginseng in the continuous cropping field.

Trichoderma panacis sp. nov., an endophyte isolated from Panax notoginseng.

An endophytic member of the genus Trichoderma was isolated from the root of a healthy 3-year-old Panax notoginseng in Yunnan province, PR China. The results of phylogenetic analyses based on a combined of ITS, tef1 and rpb2 indicated that this isolate was distinct from other species of the genus Trichoderma and closely related to Trichoderma songyi. It can be distinguished from T. songyi by its slower growth rates on PDA and colony morphology. The novel isolate formed conidia in thick white pustules scattered mostly at the margin. Its conidiophores tended to be regularly verticillium-like, little branched, sometimes substituted by phialides singly or in whorls. Conidia are smooth, mostly broadly subglobose to ellipsoidal. In combination with the genotypic and phenotypic characteristics, all data demonstrated that the fungus studied represented a unique and distinguishable novel species of the genus Trichoderma, for which the name Trichoderma panacis sp. nov. is proposed.