Search Results (11)

This study explores the biodegradation of polyhydroxybutyrate (PHB), polylactide (PLA), and their blends by 11 bacterial species (including Antarctic strains) and 6 fungal species. Aeration significantly enhanced PHB degradation by mold fungi (Aspergillus oryzae, Penicillium chrysogenum) and bacteria (Paenibacillus tundrae, Bacillus mycoides), while Aspergillus awamori was most effective under non-aerated conditions. For PLA, degradation peaked under aeration with Penicillium chrysogenum and Bacillus subtilis. PHB/PLA blends degraded slower overall, with maximum degradation under aeration by Penicillium chrysogenum, Pseudoarthrobacter sp., and Flavobacterium sp. Biodegradation was assessed via weight-loss measurements, X-ray diffraction (XRD), and thermal analysis. PHB samples showed reduced crystallinity and thermal stability linked to weight loss, while PLA samples exhibited varied changes, often with increased crystallinity and stability depending on the microorganism. PHB/PLA blends displayed variable crystallinity changes, generally decreasing under microbial action. The search for effective plastic-degrading microorganisms, particularly from extreme environments like Antarctica, is vital for addressing plastic pollution and advancing sustainable polymer degradation. Full article

Photo-microbes are well known to demolish rice and fruits, as farmers use chemical pesticides to overcome agricultural problems and economic damage. The use of pesticides in agriculture fails to protect crops in lower concentrations and increases the intake of chemicals that cause many human ailments. The sophisticated nanotechnology approach used in agriculture for antimicrobial activities offers several advantages for growth and improves nutrient absorption in plants. We report the green synthesis of silver nanoparticles (AgNPs) using Azadirachta indica (A. indica) and Mangifera indica (M. indica) tree leaf extract that contains antioxidants to treat numerous diseases. AgNPs tested against three plant pathogens, fungi Alternaria alternata (A. alternata), Sclerotium rolfsii (A. rolfsii), and bacteria Xanthomonas oryzae (X. oryzae), which leads to agricultural problems. The experiment was performed with different concentrations of AgNPs in μL/mL prepared using two other plants extract against fungi and bacteria during summer. The results expose the importance of plant extract in synthesizing silver nanoparticles (AgNPs) and their efficacy for microbes. A comparison among different concentrations of AgNPs (4 μL/mL, 6 μL/mL, and 10 μL/mL) was performed for two fungi (tomato disease) and bacteria (rice leaf blight disease). A-AgNPs (A. indica-AgNPs) demonstrate a greater zone of inhibition than M-AgNPs (M. indica-AgNPs), further highlighting the dependence of plants. Under in vitro conditions, the results of the antifungal activity showed zones of inhibition of 21 mm against A. alternata and 17 mm against A. rolfsii, while antibacterial activity against X. oryzae bacteria showed a 15 mm zone of inhibition at 10 mg/mL for A-AgNPs, and less for M-AgNPs. For AgNPs, the antifungal activity was characterized bya more significant area of inhibition than antibacterial activity was. The current study indicates that AgNPs with lower concentrations exhibitsuperior toxicity to microbes and may be able to manage diseases in rice and tomato, and increase plant growth. Full article

Rice is the most important staple food crop feeding more than 50% of the world’s population. Rice blast is the most devastating fungal disease, caused by Magnaporthe oryzae (M. oryzae) which is widespread in rice growing fields causing a significant reduction in the yield. The present study was initiated to evaluate the effect of green synthesized silver nanoparticles (AgNPs) on the biochemical constituents of rice plants infected with blast. AgNPs were synthesized by using Azadirachta indica leaf extract and their characterization was performed using UV-visible spectroscopy, particle size analyser (PSA), scanning electron microscope (SEM), and X-ray diffraction (XRD) which confirmed the presence of crystalline, spherical shaped silver nanoparticles with an average size of 58.9 nm. After 45 days of sowing, artificial inoculation of rice blast disease was performed. After the onset of disease symptoms, the plants were treated with AgNPs with different concentrations. Application of nanoparticles elevated the activity of antioxidative enzymes such as superoxide dismutase, catalase, peroxidase, glutathione reductase, and phenylalanine ammonia-lyase compared to control plants, and total phenol and reducing sugars were also elevated. The outcome of this study showed that an increase in all biochemical constituents was recorded for A. indica silver nanoparticles-treated plants. The highest values were recorded in 30 ppm and 50 ppm AgNPs-treated plants, which showed the highest resistance towards the pathogen. Green synthesized AgNPs can be used in future for disease control in susceptible varieties of rice. The synthesized AgNPs using A. indica leaf extract have shown promising antibacterial activity when tested against 14 multidrug-resistant (MDR) bacteria comprising Gram-negative bacteria Escherichia coli (n = 6) and Klebsiella pneumoniae (n = 7) with a good zone of inhibition diameter, tested with the disc diffusion method. Based on these findings, it appears that A. indica AgNPs have promise as an antibacterial agent effective against MDR pathogens. Full article

Actinomycetes play a vital role as one of the most important natural resources for both pharmaceutical and agricultural applications. The actinomycete strain SPRI-371, isolated from soil collected in Jiangsu province, China, was classified as Streptomyces aureus based on its morphological, physiological, biochemical and molecular biological characteristics. Its bacterial activity metabolites were identified as aureonuclemycin (ANM), belonging to adenosine derivatives with the molecular formula C₁₆H₁₉N₅O₉ for ANM A and C₁₀H₁₃N₅O₃ for ANM B. Simultaneously, the industrial fermentation process of a mutated S. aureus strain SPRI-371 was optimized in a 20 m³ fermentation tank, featuring a rotation speed of 170 rpm, a pressure of 0.05 MPa, an inoculum age of 36–40 h and a dissolved oxygen level maintained at 1–30% within 40–80 h and at >60% in the later period, resulting in an ANM yield of >3700 mg/L. In the industrial separation of fermentation broth, the sulfuric acid solution was selected to adjust pH and 4# resin was used for adsorption. Then, it was resolved with 20% ethanol solution and concentrated in a vacuum (60–65 °C), with excellent results. Antibacterial experiments showed that ANM was less active or inactive against Xanthomonas oryzae pv. oryzae, Xanthomonas citri subsp. citri and Xanthomonas oryzae pv. oryzicola and most bacteria, yeast and fungi in vitro. However, in vivo experiments showed that ANM exhibited extremely significant protective and therapeutic activity against diseases caused by X. oryzae pv. oryzae and X. oryzae pv. oryzicola in rice and X. citri in oranges and lemons. In field trials, ANM A 150 gai/ha + ANM B 75 gai/ha exhibited excellent therapeutic activity against rice bacterial leaf blight, citrus canker and rice bacterial leaf streak. Furthermore, as the dosage and production cost of ANM are lower than those of commercial drugs, it has good application prospects. Full article

Phage therapy is a promising biocontrol management on plant diseases caused by bacterial pathogens due to its specificity, efficiency and environmental friendliness. The emergence of natural phage-resistant bacteria hinders the application of phage therapy. Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of the devastating bacterial leaf blight disease of rice. Here, we obtained a spontaneous mutant C2R of an Xoo strain C2 showing strong resistance to the lytic phage X2. Analysis of the C2R genome found that the CDS2289 gene encoding glycosyltransferase acquired a frameshift mutation at the 180th nucleotide site, which also leads to a premature stop mutation at the 142nd amino acid. This mutation confers the inhibition of phage adsorption through the changes in lipopolysaccharide production and structure and bacterial surface morphology. Interestingly, glycosyltransferase-deficient C2R and an insertional mutant k2289 also showed reduced virulence, suggesting the trade-off costs of phage resistance. In summary, this study highlights the role of glycosyltransferase in interactions among pathogenic bacteria, phages and plant hosts, which provide insights into balanced coevolution from environmental perspectives. Full article

Xanthomonas oryzae severely impacts the yield and quality of rice. Antibiotics are the most common control measure for this pathogen; however, the overuse of antibiotics in past decades has caused bacterial resistance to these antibiotics. The agricultural context is of particular importance as antibiotic-resistant bacteria are prevalent, but the resistance mechanism largely remains unexplored. Herein, using gas chromatography–mass spectrometry (GC–MS), we demonstrated that zhongshengmycin-resistant X. oryzae (Xoo-Rzs) and zhongshengmycin-sensitive X. oryzae (Xoo-S) have distinct metabolic profiles. We found that the resistance to zhongshengmycin (ZS) in X. oryzae is related to increased fatty acid biosynthesis. This was demonstrated by measuring the Acetyl-CoA carboxylase (ACC) activity, the expression levels of enzyme genes involved in the fatty acid biosynthesis and degradation pathways, and adding exogenous materials, i.e., triclosan and fatty acids. Our work provides a basis for the subsequent control of the production of antibiotic-resistant strains of X. oryzae and the development of coping strategies. Full article

Cyclic diguanylate monophosphate (c-di-GMP) is a secondary messenger present in bacteria. The GGDEF-domain proteins can participate in the synthesis of c-di-GMP as diguanylate cyclase (DGC) or bind with c-di-GMP to function as a c-di-GMP receptor. In the genome of Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of bacterial blight of rice, there are 11 genes that encode single GGDEF domain proteins. The GGDEF domain protein, PXO_02019 (here GdpX6 [GGDEF-domain protein of Xoo6]) was characterized in the present study. Firstly, the DGC and c-di-GMP binding activity of GdpX6 was confirmed in vitro. Mutation of the crucial residues D⁴⁰³ residue of the I site in GGDEF motif and E⁴¹¹ residue of A site in GGDEF motif of GdpX6 abolished c-di-GMP binding activity and DGC activity of GdpX6, respectively. Additionally, deletion of gdpX6 significantly increased the virulence, swimming motility, and decreased sliding motility and biofilm formation. In contrast, overexpression of GdpX6 in wild-type PXO99^A strain decreased the virulence and swimming motility, and increased sliding motility and biofilm formation. Mutation of the E⁴¹¹ residue but not D⁴⁰³ residue of the GGDEF domain in GdpX6 abolished its biological functions, indicating the DGC activity to be imperative for its biological functions. Furthermore, GdpX6 exhibited multiple subcellular localization in bacterial cells, and D⁴⁰³ or E⁴¹¹ did not contribute to the localization of GdpX6. Thus, we concluded that GdpX6 exhibits DGC activity to control the virulence, swimming and sliding motility, and biofilm formation in Xoo. Full article

Biosynthesis of silver nanoparticles (AgNPs) using endophytic bacteria is a safe alternative to the traditional chemical method. The purpose of this research is to biosynthesize AgNPs using endophytic bacterium Bacillus endophyticus strain H3 isolated from onion. The biosynthesized AgNPs with sizes from 4.17 to 26.9 nm were confirmed and characterized by various physicochemical techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV-visible spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in addition to an energy dispersive spectrum (EDS) profile. The biosynthesized AgNPs at a concentration of 40 μg/mL had a strong antifungal activity against rice blast pathogen Magnaporthe oryzae with an inhibition rate of 88% in mycelial diameter. Moreover, the biosynthesized AgNPs significantly inhibited spore germination and appressorium formation of M. oryzae. Additionally, microscopic observation showed that mycelia morphology was swollen and abnormal when dealing with AgNPs. Overall, the current study revealed that AgNPs could protect rice plants against fungal infections. Full article

A series of new N-phenylacetamide derivatives containing 4-arylthiazole moieties was designed and synthesized by introducing the thiazole moiety into the amide scaffold. The structures of the target compounds were confirmed by ¹H-NMR, ¹³C-NMR and HRMS. Their in vitro antibacterial activities were evaluated against three kinds of bacteria—Xanthomonas oryzae pv. Oryzae (Xoo), Xanthomonas axonopodis pv. Citri (Xac) and X.oryzae pv. oryzicola (Xoc)—showing promising results. The minimum 50% effective concentration (EC₅₀) value of N-(4-((4-(4-fluoro-phenyl)thiazol-2-yl)amino)phenyl)acetamide (A₁) is 156.7 µM, which is superior to bismerthiazol (230.5 µM) and thiodiazole copper (545.2 µM). A scanning electron microscopy (SEM) investigation has confirmed that compound A₁ could cause cell membrane rupture of Xoo. In addition, the nematicidal activity of the compounds against Meloidogyne incognita (M. incognita) was also tested, and compound A₂₃ displayed excellent nematicidal activity, with mortality of 100% and 53.2% at 500 μg/mL and 100 μg/mL after 24 h of treatment, respectively. The preliminary structure-activity relationship (SAR) studies of these compounds are also briefly described. These results demonstrated that phenylacetamide derivatives may be considered as potential leads in the design of antibacterial agents. Full article

The initiative strategy for the development of novel anti-microbial agents usually uses the virulence factors of bacteria as a target, without affecting their growth and survival. The type III secretion system (T3SS), one of the essential virulence factors in most Gram-negative pathogenic bacteria because of its highly conserved construct, has been regarded as an effective target that developed new anti-microbial drugs. Xanthomonas oryzae pv. oryzae (Xoo) causes leaf blight diseases and is one of the most important pathogens on rice. To find potential anti-virulence agents against this pathogen, a number of natural compounds were screened for their effects on the T3SS of Xoo. Three of 34 compounds significantly inhibited the promoter activity of the harpin gene, hpa1, and were further checked for their impact on bacterial growth and on the hypersensitive response (HR) caused by Xoo on non-host tobacco plants. The results indicated that treatment of Xoo with CZ-1, CZ-4 and CZ-9 resulted in an obviously attenuated HR without affecting bacterial growth and survival. Moreover, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis showed that the expression of the Xoo T3SS was suppressed by treatment with the three inhibitors. The mRNA levels of representative genes in the hypersensitive response and pathogenicity (hrp) cluster, as well as the regulatory genes hrpG and hrpX, were reduced. Finally, the in vivo test demonstrated that the compounds could reduce the disease symptoms of Xoo on the rice cultivar (Oryza sativa) IR24. Full article

Xanthomonas oryzae pv. oryzae, which causes rice bacterial blight, is one of the most destructive pathogenic bacteria. Biological control against plant pathogens has recently received increasing interest. 1-Deoxy-N-acetylglucosamine (1-DGlcNAc) was extracted from the supernatant of Virgibacillus dokdonensis MCCC 1A00493 fermentation through antibacterial bioassay-guided isolation. Its structure was elucidated by LC/MS, NMR, chemical synthesis and time-dependent density functional theory (TD-DFT) calculations. 1-DGlcNAc specifically suppressed X. oryzae pv. oryzae PXO99A (MIC was 23.90 μg/mL), but not other common pathogens including Xanthomonas campestris pv. campestris str.8004 and Xanthomonas oryzae pv. oryzicola RS105. However, its diastereomer (2-acetamido-1,5-anhydro-2-deoxy-d-mannitol) also has no activity to X. oryzae pv. oryzae. This result suggested that activity of 1-DGlcNAc was related to the difference in the spatial conformation of the 2-acetamido moiety, which might be attributed to their different interactions with a receptor. Eighty-four unique proteins were found in X. oryzae pv. oryzae PXO99A compared with the genome of strains8004 and RS105 by blastp. There may be unique interactions between 1-DGlcNAc and one or more of these unique proteins in X. oryzae pv. oryzae. Quantitative real-time PCR and the pharmMapper server indicated that proteins involved in cell division could be the targets in PXO99A. This research suggested that specificity of active substance was based on the active group and spatial conformation selection, and these unique proteins could help to reveal the specific mechanism of action of 1-DGlcNAc against PXO99A. Full article