Isolation of Bioactive Compounds, Antibacterial Activity, and Action Mechanism of Spore Powder From Aspergillus niger xj

Abstract

Aspergillus fungi can produce a wide range of secondary metabolites, and they have represented a potential resource of novel bioactive compounds. Bacterial plant diseases have a serious impact on the sustainable development of agriculture worldwide, so it is necessary to use natural antibacterial compounds in microorganisms to control plant pathogens. This study was conducted to investigate the bioactive compounds of Aspergillus niger xj, three plant pathogens (Agrobacterium tumefaciens T-37, Erwinia carotovora EC-1, and Ralstonia solanacearum RS-2) were used as indicator bacteria, according to the biological activity tracking, five compounds were isolated from A. niger xj spore powder, and characterization of compounds was done by NMR (1H-NMR and 13C-NMR) and EI-MS and was identified as ergosterol (1), β-sitosterol (2), 5-pentadecylresorcinol (3), 5-hydroxymethyl-2-furancarboxylic acid (4), and succinimide (5). Compounds 3 and 5 were isolated from A. niger xj for the first time. The minimum inhibitory concentration (MIC) of five compounds against three plant pathogens was evaluated, the results showed that compound 4 exhibited the strongest antibacterial activity against tested bacteria, and RS-2 was the most sensitive to compound 4, showing the lowest MIC of 15.56 μg/ml. We concluded that the mechanism of action of the compound 4 against RS-2 might be described as compound 4 acting on bacterial protein synthesis and intracellular metabolism according to the results of the scanning electron microscopy observation, permeability of cell membrane and SDS-PAGE. These results indicated that compound 4 has good potential to be as a biocontrol agent. In conclusion, the results from this study demonstrated that the compounds with antibacterial activity are of great significance of the prevention and control of plant phytopathogenic bacteria, and they may be applicable to exploring alternative approaches to integrated control of phytopathogens.

Antagonistic effects of Talaromyces muroii TM28 against Fusarium crown rot of wheat caused by Fusarium pseudograminearum

“…DWF5 (HYE68_001781), CYP51 (HYE68_002214), and cycloeucalenol cycloisomerase (HYE68_005067), which are involved in steroid synthesis, were significantly downregulated. The cell membrane plays an important role in the transport of osmoprotective compounds ( Liu et al, 2018 ), and an increase in cell membrane permeability causes the leakage of intracellular substances and an increase in electrical conductivity, leading to cell death ( Furuya et al, 2011 ; Wei et al, 2022 ). The present study demonstrated that the electrical conductivity of the Fp fermentation broth was significantly higher after TM28 treatment compared to the control ( Figure 3A ), suggesting that the metabolites produced by TM28 affected the membrane permeability of Fp .…”

Antioxidant and Antibacterial Activity of Endophytic Fungi Isolated from The Leaves of Sungkai (Peronema canescens)

“…The hydroxyl and carbonyl groups contained in the compound cause antioxidant and antibacterial activity. [61][62][63] The ethyl acetate extract of A. niger showed very strong antioxidant activity with an IC50 value close to ascorbic acid (IC50 < 20 µg/mL). Its antibacterial activity is in the strong category against the four test bacteria.…”

Antimicrobial Action Mechanisms of Natural Compounds Isolated from Endophytic Microorganisms

“…Among these compounds, 47 has exhibited antibacterial activity against Ralstonia solanacearum RS-2, with an MIC value of 15.56 μg/mL. SEM, assessment of the cell membrane permeability, and SDS-PAGE analysis have determined that the mechanism of action of 47 involves the inhibition of bacterial protein synthesis and intracellular metabolism [ 90 ].…”

“…The endophytic fungus Pestalotia sp., isolated from the leaves of Heritiera fomes, has yielded two compounds: oxysporone (89) and xylitol (90). These compounds demonstrate antibacterial activities against various strains of methicillin-resistant S. aureus, including ATCC 25923, SA-1199B, RN4220, XU212, EMRSA-15, and EMRSA-16.…”