Effect of soil bioremediation on soil microbial community structure aimed at controlling tobacco bacterial wilt.

Rebuilding soil healthy microbiota is very important for preventing bacterial wilt. A 3-year-long field trial was conducted in China as follows: T1 (conventional fertilization), T2 (T1 + liming), T3 (T1 + bioorganic fertilizer), and T4 (T2 + bioorganic fertilizer). Fluorescence quantitative PCR and high-throughput sequencing were employed to study the dynamics of Ralstonia solanacearum population, microbial community, and network organizations between bacteria and quality-related variables. After 3 years of bioremediation, the control efficacy of tobacco bacterial wilt reached 61.30% and the occurrence delayed by approximately 40 days in T4, which had the highest tobacco yield and output value. The pathogen population of T4 remained below 106 copies/g soil during the entire growth period. Role-shifts prevailed among the network members. Microbes were unipathically associated with variables in T1 but multiplex in T4. In conclusion, soil bioremediation rebuilds a healthy soil microbiota and forms a more interactive and relevant micro-system, thus effectively controlling tobacco bacterial wilt. KEY POINTS: • This is the first time to effectively bio-control tobacco bacterial wilt in practical production in China, as well as to high-efficiently use the organic waste, thus promoting the organic cycling of the environment. • Soil bioremediation can effectively control soil-borne disease by rebuilding soil healthy microbiota and reducing abundance of pathogenic bacteria, thereby to prevent the soil borne disease occurrence. • After the soil remediated, microbes associated with soil and tobacco characteristics changed from unipathical to multiplex, and the keystone species play different roles compared with the original soil, thus signifying the complexity of multi-species interactions and achieving a closely relevant micro-system, which was ecologically meaningful to the environment.

Enhanced and sustained pesticidal activity of a graphene-based pesticide delivery system against the diamondback moth Plutella xylostella.

BACKGROUND: Traditional abamectin (Abm) formulations have several shortcomings, such as low water solubility, burst release behavior, poor photostability, and short persistence periods, which decrease their pesticidal activity and the risks they pose to the environment. Nanomaterial-based pesticide delivery systems (PDSs) provide new strategies for the efficient and safe application of pesticides. Here, we developed Abm-loaded graphene oxide (Abm/GO) as a PDS for the sustained release of Abm, which shows enhanced control efficacy against Plutella xylostella. RESULTS: The hydrophobic Abm molecule was effectively loaded on GO nanocarrier by a physisorption method, which formed a uniform and stable Abm/GO nanoformulation. GO possesses high adsorption capacity and can effectively load Abm. The Abm/GO nanoformulation shows enhanced water dispersion stability and can remain stable during a 2-year storage period in contrast to the water-insoluble Abm. In addition, the Abm/GO nanoformulation exhibits sustained pesticide release behavior and possesses significantly improved anti-ultraviolet properties. Thus, the Abm/GO nanoformulation shows superior pesticidal activity compared with Abm. Abm/GO showed negligible toxicity to maize seedlings, and its GO nanocarrier can reduce the cytotoxicity of Abm to A549 cells. CONCLUSION: GO-based PDSs can effectively overcome the disadvantages of traditional pesticides, such as their insolubility, burst release behavior, instability, and short persistence period. GO shows much future promise in agriculture in light of its industrialization potential. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

5-Aminosalicylic acid ameliorates dextran sulfate sodium-induced colitis in mice by modulating gut microbiota and bile acid metabolism.

Colitis develops via the convergence of environmental, microbial, immunological, and genetic factors. The medicine 5-aminosalicylic acid (5-ASA) is widely used in clinical practice for colitis (especially ulcerative colitis) treatment. However, the significance of gut microbiota in the protective effect of 5-ASA on colitis has not been explored. Using a dextran sulfate sodium (DSS)-induced colitis mouse model, we found that 5-ASA ameliorated colitis symptoms in DSS-treated mice, accompanied by increased body weight gain and colon length, and a decrease in disease activity index (DAI) score and spleen index. Also, 5-ASA alleviated DSS-induced damage to colonic tissues, as indicated by suppressed inflammation and decreased tight junction, mucin, and water-sodium transport protein levels. Moreover, the 16S rDNA gene sequencing results illustrated that 5-ASA reshaped the disordered gut microbiota community structure in DSS-treated mice by promoting the abundance of Bifidobacterium, Lachnoclostridium, and Anaerotruncus, and reducing the content of Alloprevotella and Desulfovibrio. Furthermore, 5-ASA improved the abnormal metabolism of bile acids (BAs) by regulating the Farnesoid X receptor (FXR) and Takeda G-protein-coupled receptor 5 (TGR5) signaling pathways in DSS-treated mice. In contrast, 5-ASA did not prevent the occurrence of colitis in mice with gut microbiota depletion, confirming the essential role of gut microbiota in colitis treatment by 5-ASA. In conclusion, 5-ASA can ameliorate DSS-induced colitis in mice by modulating gut microbiota and bile acid metabolism. These findings documented the new therapeutic mechanisms of 5-ASA in clinical colitis treatment.

First Report of Leaf Spot Disease caused by Nigrospora oryzae on Nicotiana tabacum in China.

Tobacco (Nicotiana tabacum) is an important economic crop and widely cultivated in rural areas in south of China. A previously uncharacterized disease was observed on field-grown tobacco during 2020 and 2021 around Tongren city, Guizhou province of China (27°59'25.73" N, 108°7'2.43" E). The disease mainly occurred from fast growing period (about 13-16 leaves) to leaf maturity stage. In severely diseased areas, the incidence rate was between 20%-100%. Symptoms first began as yellow-brown necrotic spots on leaves, then merged into larger irregular necrotic spots surrounded by chlorotic halos. Similar lesions were also found on the stems. Ten symptomatic leaf and stem samples were collected from the different infected plants for pathogen isolation. The small pieces of discolored tissues were surface-disinfected with 2% sodium hypochlorite for 3 min and 75% ethanol for 30 s, rinsed three times with sterile water, and blotted on sterile filter paper, placed on potato dextrose agar thenincubated at 28°C in the dark for 3-4 days. The obtained isolates were purified through single-spore culture. Colonies were initially white and fluffy in appearance, later turning gray. Hyphae were smooth, branched, septa, transparent or light brown. Spores were solitary, oblate or nearly spherical, dark brown to black, smooth, 14.3 to 16.1µm × 11.8 to 15.2 µm in diameter. DNA of fungal isolates were extracted using Fungi Genomic DNA Extraction Kit (Solarbio, Beijing, China), the internal transcribed spacer (ITS) of the ribosomal DNA, ß-tubulin (TUB2) gene and translation elongation factor 1-alpha (TEF1-α) were amplified with primers ITS1/ITS4, ßt2a/ßt2b and EF1-1728F/EF1-986R, respectively. The resulting ITS, TUB2 and TEF1-α sequences were deposited at GenBank, NCBI under accessions MZ882151, MZ927749, MZ927747, respectively. The sequence identity of ITS, TUB2 and TEF1-α with those of Nigrospora oryzae strains HBN (KU254608), HGUP191068 (MZ724102) and LC7307 (KY019409) were 99.64%, 99.29% and 99.65%, respectively. Based on morphological features and phylogenetic analysis, the pathogen was identified as N. oryzae (Wang et al. 2017). Pathogenicity tests were conducted by placing agar plugs-containing fungal mycelia and agar blocks (control) on leaves of tobacco plants grown at 28°C with 60% humidity in greenhouse. Symptoms appeared on the pathogen inoculated leaves seven days after inoculation, whereas the control treatment remained symptomless. The pathogens were reisolated from diseased leaves and identified as N. oryzae based on morphological, molecular and phylogenetic analysis, which were fulfilling Koch's postulates. This pathogen was recently identified from watermelon and kiwifruit in the Guizhou (Far and Rossman, 2021). To our knowledge, this is the first report of leaf spot caused by N. oryzae on Nicotiana tabacum in China.

Plasma metabolomic profiles reveal regulatory effect of chitosan oligosaccharides on loperamide-induced constipation in mice.

Chitosan oligosaccharides (COS) can improve the symptoms of constipation. In this study, we further explored the regulator effect of COS on aberrant plasma metabolomics in constipated mice. Using untargeted metabolomic analysis by ultra-performance liquid chromatography-mass spectrometer (UPLC-MS), we identified several most significantly changed metabolic pathways in plasma of constipated mice induced by loperamide, including those correlated with the metabolisms of sphingolipid, glycerophospholipid, tryptophan, bile acids, unsaturated fatty acids, and amino acids. The changes in these metabolic pathways were reversed by COS treatment largely. Furthermore, the mRNA levels of some key target genes related to the above metabolic pathways in colon samples were detected by reverse transcription-polymerase chain reaction analysis. We showed that COS significantly suppressed the abnormal expression of these genes, including ceramide glucosyltransferase (CGT), sphingolipid 4-desaturase (DEGS2), alkaline ceramidase (ACER1), sphingosine kinase 2 (SPHK2), lysophosphatidylcholine acyltransferase (LPCAT1), and aromatic-L-amino-acid (DDC). These data provide insight into the mechanisms by which COS ameliorates loperamide-induced constipation in mice.

Host Deprivation Effects on the Functional Response and Parasitism Rate of Habrobracon hebetor (Hymenoptera: Braconidae) on Ephestia elutella (Lepidoptera: Pyralidae) in the Laboratory.

Habrobracon hebetor (Say) is an important biological control agent for lepidopteran pests of stored products. In this study, the age-specific functional response, paralysis rate, and parasitism rate of H. hebetor under different host deprivation treatments (PC: without host deprivation, used as the control, P1d: host deprivation, but the host was removed after 1 d contact, and PW: host deprivation from beginning) were evaluated at different larval densities (5, 10, 20, 40, and 80) of the Ephestia elutella (Hübner) at 28 ± 1°C, 75 ± 5% RH and 16:8 h L:D. Ages of parasitoid females used were 2, 5, 10, and 20 d old. The logistic regression results indicated that the functional response of H. hebetor females under different host deprivation treatments was type II. The longest handling time was observed in 20-d old females, while the shortest handling time and highest maximum attack rate (T/Th) were estimated at the age of 2 d in all treatments. The paralysis and parasitism rates of H. hebetor were the highest at 2, 5, and 10-d old in all treatments. The results of this study suggest that H. hebetor females up to 10-d old can be used as an efficient biological control agent against E. elutella. The data of this study can also be used to predict the efficacy of different aged H. hebetor females in controlling E. elutella populations.

Modulation of gut microbiota and intestinal metabolites by lactulose improves loperamide-induced constipation in mice.

Lactulose is a common laxative and has been widely applied to clinical treatment for constipation. This study aimed to explore the improving effect of lactulose on constipation through the mediation of gut microbiota and intestinal metabolites. BALB/c mice with constipation induced by loperamide were orally treated with lactulose for four weeks. After the treatment, the constipation-related factors were determined. The effect of lactulose on the composition of gut microbiota was assessed by 16S rDNA gene sequencing. Gas chromatography or liquid chromatography-mass spectrometer (GC/LC-MS) analysis was used for the quantification of intestinal metabolites. The treatment of constipated mice with lactulose accelerated intestinal motility, suppressed inflammatory responses, protected gut barrier, and improved metabolisms of water and salt in the intestinal tract. These therapeutic effects were attributed to the reversed gut microbiota dysfunction, which conferred the benefit to the production of intestinal metabolites including bile acids, short-chain fatty acids, and tryptophan catabolites. Further, the depletion of intestinal flora from loperamide- or (loperamide + lactulose)-treated mice confirmed the significance of gut microbiota in the mediation of constipation. In summary, this study leads us to propose that lactulose may improve constipation through a prebiotic effect on gut microbiota and intestinal metabolites.

Chitosan oligosaccharides attenuate loperamide-induced constipation through regulation of gut microbiota in mice.

This study was designed to explore the improvement of chitosan oligosaccharides (COS) on constipation through regulation of gut microbiota. Here, we proved that COS treatment profoundly boosted intestinal motility, restrained inflammatory responses, improved water-electrolyte metabolism and prevented gut barrier damage in constipated mice induced by loperamide. By 16S rDNA gene sequencing, the disbalanced gut microbiota was observed in constipated mice, while COS treatment statistically reversed the abundance changes of several intestinal bacteria at either phylum, family and genus levels, which partly led to the balance in production of intestinal metabolites including bile acids, short-chain fatty acids and tryptophan catabolites. In addition, COS failed to relieve the constipation in mice with intestinal flora depletion, confirming the essentiality of gut microbiota in COS-initiated prevention against constipation. In summary, COS can ameliorate the development of loperamide-induced constipation in mice by remodeling the structure of gut microbial community.