Transcriptome analysis reveals the inhibitory mechanism of 3,4-Dimethoxyphenol from Streptomyces albidoflavus strain ML27 against Xanthomonas oryzae pv. oryzae.

Bacterial leaf blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), poses a significant threat to rice cultivation across diverse regions. Growing concerns about pesticide resistance and environmental impact underscore the urgent necessity for eco-friendly biopesticides. Here, the complete genome sequence of Streptomyces albidoflavus strain ML27 revealed substantial antimicrobial activity and secondary metabolite production potential through genome mining. 3,4-dimethoxyphenol (purity 97%) was successfully isolated from the fermentation broth of S. albidoflavus strain ML27, exhibiting broad and pronounced inhibitory effects on the growth of seven different fungi and five tested bacteria. The efficacy of 3,4-dimethoxyphenol in controlling rice bacterial leaf blight was evaluated through pot tests, demonstrating substantial therapeutic (69.39%) and protective (84.53%) effects. Application of 3,4-dimethoxyphenol to Xoo resulted in cells displayed notable surface depressions, wrinkles, distortions, or even ruptures compared to their typical morphology. Transcriptome analysis revealed significant inhibition of membrane structures, protein synthesis and secretion, bacterial secretion system, two-component system, flagellar assembly, as well as various metabolic and biosynthetic pathways by 3,4-dimethoxyphenol. Notably, the down-regulation of the type III secretion system (T3SS) expression was a pivotal finding. Furthermore, validation via quantitative real-time polymerase chain reaction (qRT-PCR) analysis confirmed significant downregulation of 10 genes related to T3SS upon 3,4-dimethoxyphenol treatment. Based on these results, it is promising to develop 3,4-dimethoxyphenol as a novel biopesticide targeting the T3SS of Xoo for controlling bacterial leaf blight in rice.

Inhibitory mechanism of 4-ethyl-1,2-dimethoxybenzene produced by Streptomyces albidoflavus strain ML27 against Colletotrichum gloeosporioides.

Actinomycetes have emerged as significant biocontrol resources due to their rich array of bioactive natural products. While much research has historically focused on secondary metabolites isolated from their fermentation broth, there remains a dearth of reports on their volatile organic compounds (VOCs). Here, strain ML27, isolated from soil, was identified as Streptomyces albidoflavus based on morphological features, physiological, biochemical, and molecular characteristics (16S rRNA, atpD, recA, and rpoB gene sequences). VOCs from S. albidoflavus strain ML27 were effectively captured using solid-phase microextraction (SPME) and tentatively identified through gas chromatography-mass spectrometry (GC/MS). Among these compounds, 4-ethyl-1,2-dimethoxybenzene exhibited broad-spectrum antifungal activity and demonstrated efficacy in controlling citrus anthracnose, with a control efficacy of 86.67%. Furthermore, the inhibitory mechanism of 4-ethyl-1,2-dimethoxybenzene against Colletotrichum gloeosporioides was revealed. Results indicated that 4-ethyl-1,2-dimethoxybenzene induced swelling, deformity, and breakage in C. gloeosporioides mycelia, and significantly inhibited spore germination. Transcriptome analysis revealed that 4-ethyl-1,2-dimethoxybenzene inhibited the growth and development of C. gloeosporioides primarily by disrupting energy metabolism and the integrity of the cell wall and membrane. Based on these results, it is promising to develop 4-ethyl-1,2-dimethoxybenzene as a novel biopesticide for controlling citrus anthracnose.

First Report of Diaporthe phoenicicola causing leaf spot on blueberry (Vaccinium virgatum) in China.

Blueberry (Vaccinium virgatum), a member of the Ericaceae family, is an increasingly important crop in China because of its abundant nutritional benefits and economic value (Kuzmanovic et al. 2019). In October 2021, leaf spots were detected on 'Rabbiteye' blueberry at the Agricultural Science and Technology Park of Jiangxi Agricultural University in Nanchang, China (28°45'51"N, 115°50'52"E), which caused severe defoliation of the crop and fruit yield losses of 25% (Figure 1A). Disease surveys were conducted at that time; the results showed that disease incidence was 75.5%, observed in 151 of the 200 accessions sampled, and this disease had not been found at other cultivation fields in Nanchang. Lesions with taupe to dark brown margins were irregularly shaped and associated with leaf margins. Spots coalesced to form larger lesions, with black pycnidia present in more mature lesions. To identify the causal agent, 10 small pieces (5 mm2) of leaf tissue excised from the lesion margins were surface sterilized in 75% ethanol solution for 30 s and 0.1% mercuric chloride solution for 2 min, rinsed three times with sterile distilled water, then placed on potato dextrose agar (PDA) at 25°C for 5 to 7 days in darkness. Five fungal isolates showing similar morphological characteristics were obtained as pure cultures by single-spore isolation. All fungal colonies on PDA were floccose, dense, and white (Figure 1B.C). Black pycnidia developed on PDA at 25°C under a 12/12 h light/dark cycle for 30 days. Alpha conidia were 6.17 to 8.53 × 1.64 to 3.20 µm (average 6.94 × 2.52 µm, n = 100), aseptate, hyaline, fusiform to ellipsoidal, often biguttulate. Beta conidia were 15.26 to 25.41 × 0.92 to 1.40 µm (average 20.14 × 1.27 µm, n = 30), aseptate, hyaline, linear to hamate (Figure 1D). Based on morphological characteristics, the fungal isolates were suspected to be Diaporthe spp. (Gomes et al. 2013). To further confirm the identity of this putative pathogen, two representative isolates (LGM1 and LGM2) were selected for molecular identification. The internal transcribed spacer region (ITS), translation elongation factor 1α (EF1-α), histone H3 (HIS), calmodulin (CAL), and ß-tubulin (TUB2) genes were amplified from gDNA and sequenced using primers ITS1/ITS4 (Peever et al. 2004), EF1-728F/EF1-986R and CAL228F/CAL737R (Carbone et al. 1999), CYLH3F/H3-1b (Crous et al. 2004), Bt2a/Bt2b (Glass and Donaldson 1995), respectively. GenBank accession numbers of isolate LGM1 and LGM2 were OM778771 to 72 for the ITS region, OM868228 to 29 for EF1-α, OM837771 to 72 for TUB2, ON206971 to 72 for CAL, ON206973 to 74 for HIS. BLAST results showed that the ITS, EF1-α, TUB2, HIS, and CAL sequences showed 99% (538/545 bp), 100% (322/322 bp), 99% (480/484 bp), 99% (459/460 bp), 99% (430/433 bp) identity, respectively, with those of Diaporthe phoenicicola (GenBank accession no. MW504735, MW514099, MW514142, MW514067, MT409304). Two maximum likelihood phylogenetic trees were built based on the sequences of ITS, EF1-α, HIS, CAL, and TUB2 by using MEGA 5. The two isolates LGM1 and LGM2 clustered with D. phoenicicola (Figure 2 and 3). The fungus was identified as D. phoenicicola by combining morphological and molecular characteristics. To evaluate the pathogenicity, three healthy young potted V. virgatum plants were spray inoculated with a conidial suspension of 106 conidia/ml. Another set of three plants that were sprayed with sterilized distilled water served as the controls. The experiment was repeated three times, and all plants were maintained in a climate box (12 h light/dark) at 25°C with 80% relative humidity. Five days after inoculation, no symptoms were observed on control plants (Figure 1F), and all inoculated plants showed symptoms (brown flecks) similar to those observed in the field (Figure 1E). The fungus was reisolated from the infected tissues and confirmed as D. phoenicicola by morphological and molecular identification, and could not be isolated from the controls, fulfilling Koch's postulates. To our knowledge, this is the first report of D. phoenicicola causing leaf spot on blueberry in China. The discovery of this new disease and the identification of the pathogen will provide useful information for developing specific control measures and potential sources for resistance to this disease caused by D. phoenicicola.

Endophytic bacterial community diversity in two citrus cultivars with different citrus canker disease resistance.

The selective infection of Xanthomonas citri pv. citri (Xcc) to citrus cultivars is universally known, but the relationship between endophytic bacteria and the resistance of host variety to canker disease remains unclear. In this study, endophytic bacterial populations of two citrus cultivars-the resistant satsuma mandarin and the susceptible Newhall navel orange-were analyzed through high-throughput sequencing. The results showed that endophytic bacterial community of satsuma mandarin was more abundant than that of Newhall navel orange. In addition, bacterial abundance was the highest in the spring samples, followed by that in summer and winter samples, in both the varieties. In all samples, the predominant phyla were Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes; the major genera were Bacillus and Stenotrophomonas, and the main species was Bacillus subtilis. According to the analysis of the predominant bacteria in the two citrus cultivars, B. subtilis with potential antagonistic characteristics against Xcc existed universally in all samples. However, the susceptible Newhall navel oranges were abundant in Bacillus subtilis and had a relatively large number of canker-causing cooperative bacteria such as Stenotrophomonas. The results suggested that endophytic bacterial community of the two citrus cultivars had some differences based on the season or plant tissue, and these differences were mainly in the quantity of bacteria, affecting citrus canker disease occurrence. In conclusion, the differences in endophytic bacteria on citrus cultivars might be related to host resistance or susceptibility to citrus canker disease.

Synergetic conditioning via oxalic acid enhanced Fe2+/CaO2 and skeleton construct to achieve deep dewatering of sewage sludge.

Extracellular polymeric substance (EPS) with highly hydrophilic groups and sludge with high compressibility are determined sludge dewaterability. Herein, Fe2+ catalyzed calcium peroxide (CaO2) assisted by oxalic acid (OA) Fenton-like process combined with coal slime was applied to improve sludge dewaterability. Results demonstrated that the sludge treated by 0.45/1/1.1-OA/Fe2+/CaO2 mM/g DS, the water content (WC), specific resistance to filtration and capillary suction time dropped to 53.01%, 24.3 s and 1.2 × 1012 m/kg, respectively. Under coal slime ratio as 0.6, WC and compressibility were further reduced to 42.72% and 0.66, respectively. The hydroxyl radicals generated by OA/Fe2+/CaO2 under near-neutral pH layer by layer collapsed EPS, resulting in the degradation and migration of inner releasing components and the exposure of inner sludge flocs skeleton. The hydrophilic tryptophan-like protein of TB-EPS were degraded into aromatic protein of S-EPS and exposed inner hydrophobic sites. The protein secondary structures were transformed by destroying hydrophilic functional groups, which were attributed to the reducing α-helix ratio and reconstructing ß-sheet. Moreover, coal slime as the skeleton builder lowered compressibility and formed more macropores to increase the filterability of pre-oxidized sludge for the higher intensity of rigid substances. This study deepened the understanding of OA enhanced Fenton-like system effects on sludge dewaterability and proposed a cost-effective and synergistic waste treatment strategy in sludge dewatering.

Promotion of aromatic amino acids of extracellular polymeric substance targeted transformation via sulfite mediated iron redox cycling in sludge solid-liquid separation.

Highly hydrophilic extracellular polymeric substance (EPS) with gel-like structure seriously plagues the development of sludge deep dewatering. Oxysulfur radicals-based oxidation driven by iron-bearing mineral proposes a promising strategy for effective EPS decomposition. However, the transformation and involved interaction mechanisms of aromatic proteins are still controversial due to the complex EPS structure. Herein, sulfite mediated siderite (denoted as Fe(II)/S(IV)) was developed for targeted transformation aromatic amino acids in EPS oxidation to strengthen sludge solid-liquid separation. The enhanced sludge dewaterability were benefited from the Fe(II)/S(IV) bonded interaction assisted by Fe3+/Fe2+ as redox interface that facilitating the release of intracellular bound water via diminish the hydrophily and bind strength with solid protons. The amide region nitrogen of aromatic amino acids (especially tyrosine and tryptophan) originating from EPS presented looser structure and lower spatial site resistance, which were attributed to the exposure of hydrophobic sites in amino groups after Fe(II)/S(IV) treatment. Furthermore, the effective decline of aromatic amino acids in inner layer-EPS (loosely bound EPS and tightly bound EPS) was directed from Fe-N targeted interaction by triggering a series of sulfate-based radical chain reactions. The good correlation between electron transfer amount (R2 = 0.926) and Fe-N (R2 = 0.925) with bonding interaction demonstrated that the complexation of aromatic amino acids with Fe sites on siderite/sulfite via Fe-N bonds, accounting for efficient sludge solid-liquid separation. This study deepens the understanding of sludge organic matter targeted transformation and provides a tactic for iron-based conditioning of sludge.

Melatonin alleviates necrotizing enterocolitis by reducing bile acid levels through the SIRT1/FXR signalling axis.

Bile acids (BAs) have increasingly been implicated in the onset and progression of necrotizing enterocolitis (NEC); multiple findings have demonstrated their ability to induce damage to the intestinal epithelium, thereby exacerbating disease severity. Although we previously showed that melatonin was able to treat NEC by correcting the Treg/Th17 imbalance, the modulatory effect of melatonin on BAs remains unclear. In this study, we conducted transcriptome analysis on intestinal tissues from patients with NEC and validated these findings. Subsequently, we treated mice with melatonin alone or in combination with an agonist/inhibitor of Sirtuin 1 (SIRT1) to assess faecal and serum BA levels, the expression levels of BA transporters and regulators, and the extent of intestinal injury. Our transcriptome results indicated dysregulation of BA metabolism and abnormal expression of BA transporters in patients with NEC, which were also observed in our NEC mouse model. Furthermore, exogenous BAs were found to aggravate NEC severity in mice. Notably, melatonin effectively restored the aberrant expression of BA transporters, such as apical membrane sodium-dependent bile acid transporters (ASBT), ileal bile acid-binding protein (IBABP), and organic solute transporter-alpha (OST-α), by upregulating SIRT1 expression while reducing farnesoid X receptor (FXR) acetylation, consequently leading to decreased serum and faecal BA levels and mitigated NEC severity. Thus, we propose a potential mechanism through which melatonin reduces BA levels via the SIRT1/FXR signalling axis in an NEC mouse model. Collectively, these results highlight that melatonin holds promise for reducing BA levels and represents a promising therapeutic strategy for treating NEC.

Visible light and iodate/iodide mediated degradation of bisphenol A by self-assembly 3D hierarchical BiOIO3/Bi5O7I Z-scheme heterojunction: Intermediates identification, radical mechanism and DFT calculation.

Broadening the light absorption and inhibiting carrier's recombination are vital to the improvement of photocatalytic performance. Herein, self-assembly 3D hierarchical microsphere BiOIO3/Bi5O7I Z-scheme heterojunction with carrier transfer channel was firstly fabricated by in-situ solvothermal method. The degradation efficiency for bisphenol A (BPA) reached 98.9 % within 60 min visible light irradiation. The enhanced photocatalytic activity was benefited from the Z-scheme system assisted by iodate/iodide (IO3-/I-) as carrier transfer channel that not only accelerated the interfacial charge separation, but also provided massive reactive centers for obtaining high redox capacity. The vulnerable sites and the degradation pathways of BPA were identified by density functional theory calculations and liquid chromatography-mass spectrometry analyses. The toxicity of BPA and its intermediates were predicted by ECOlogical Structure Activity Relationship (ECOSAR) and the results demonstrated that BPA was eventually mineralized to harmless products. The Z-scheme charge transfer mechanism was deeply elucidated based on the role of active species (·O2-, ·OH and h+), band structure and carrier separation efficiency. This study provides a promising strategy for the photoactivity enhancement of bismuth based heterojunction in environment purification.

Insights into the role of ·OH generated in Fe2+/CaO2/coal slime system for efficient extracellular polymeric substances degradation to improve dewaterability of sewage sludge.

The disposal of massive sewage sludge and coal slime is a problem facing municipalities in China. A hypothesis for the co-disposal of sludge and coal slime is proposed to improve dewaterability by utilizing the beneficial role of coal slime as a filter assist and CaO2 enhanced system in this research. Results showed that capillary suction time, specific resistance to filtration and water content decreased dramatically from 49.3 s, 13.2 × 1012 m/kg and 84.85% to 19.1 s, 1.0 × 1012 m/kg and 50.07%, respectively, under the optimal conditions with 0.3/0.1/0.3-Fe2+/CaO2/coal slime g/g DS. The hydroxyl radicals generated in the Fe2+/CaO2 process acted on extracellular polymeric substances (EPS), resulting in a drop in the ratio of α-helix/(ß-sheet + random coil) in the secondary structure of EPS proteins and a reduction in the concentration of aromatic proteins and tryptophan-like substances in TB-EPS, thereby enhancing the sludge dewaterability. Furthermore, coal slime as the skeleton building material induced a rise in sludge particle size and contact angle, lowering the hydrophilicity, compressibility of sludge and providing more channels to facilitate water flow. This work verified the promising application prospect of the Fe2+/CaO2/coal slime combined system in the enhancement of sludge dewaterability.

Maternal melatonin supplementation shapes gut microbiota and protects against inflammation in early life.

BACKGROUND: Gut microbiota colonization is critical for immune education and nutrient metabolism. Research shows that melatonin has beneficial effects as a therapy for many diseases via modulating gut dysbiosis. However, it is unclear whether melatonin alters gut microbiota colonization in early life. METHODS: In the experimental group (Mel), mice were intraperitoneally injected with melatonin at 10 mg/kg body weight for embryonic days 14-16 and received drinking water containing 0.4 mg/mL melatonin until 28 days postpartum. In the control group (Ctrl), mice were injected with the same volume of 2.5% ethanol in saline and provided with standard water. Two more groups were created by treating neonatal mice with 20 mg/kg lipopolysaccharide (LPS) to induce inflammation, resulting in the groups Ctrl + LPS and Mel + LPS, respectively. We examined the gut microbiota of the neonatal mice in the Ctrl and Mel group on Days 7, 14, 21, and 28 post-birth. On Day 14, melatonin and short-chain fatty acids (SCFAs) concentrations were measured in the Ctrl and Mel group and the mice were treated with LPS to be evaluated for intestinal injury and inflammatory response 15 h post treatment. According to the result of the SCFAs concentrations, some neonatal mice were intraperitoneally injected with 500 mg/kg sodium butyrate (SB) from Days 11-13, intraperitoneally injected with 20 mg/kg LPS on Day 14, and then euthanized by carbon dioxide inhalation the next morning. Intestinal injury and inflammatory responses were evaluated in the Ctrl + LPS and SB + LPS groups, respectively. RESULTS: By Day 14, it was evident that maternal melatonin supplementation significantly increased the relative abundance of Firmicutes in the ileal [61.03 (35.35 - 76.18) % vs. 98.02 (86.61 - 99.01) %, P = 0.003] and colonic [73.88 (69.77 - 85.99) % vs. 96.16 (94.57 - 96.34) %, P = 0.04] microbiota, the concentration of melatonin (0.79 ± 0.49 ng/ml vs. 6.11 ± 3.48 ng/ml, P = 0.008) in the gut lumen, and the fecal butyric acid (12.91 ± 5.74 µg/g vs. 23.58 ± 10.71 µg/g, P = 0.026) concentration of neonatal mice. Melatonin supplementation, and sodium butyrate treatment markedly alleviated intestinal injury and decreased inflammatory factors in neonatal mice. CONCLUSION: This study suggests that maternal melatonin supplementation can shape the gut microbiota and metabolism of offspring under normal physiological conditions and protect them against LPS-induced inflammation in early life.