Antifungal activity of the volatile organic compounds produced by Bacillus velezensis strains against postharvest fungal pathogens

Activity assessment of tomato endophytic bacteria bioactive compounds for the postharvest biocontrol of Botrytis cinerea

Antifungal activity of volatile organic compounds produced by Pseudomonas fluorescens ZX and potential biocontrol of blue mold decay on postharvest citrus

Bacillus volatiles to control plant nematodes is a topic of great interest among researchers due to its safe and environmentally friendly nature. Bacillus strain GBSC56 isolated from the Tibet region of China showed high nematicidal activity against M. incognita, with 90% mortality as compared with control in a partition plate experiment. Pure volatiles produced by GBSC56 were identified through gas chromatography and mass spectrometry (GC-MS). Among 10 volatile organic compounds (VOCs), 3 volatiles, i.e., dimethyl disulfide (DMDS), methyl isovalerate (MIV), and 2-undecanone (2-UD) showed strong nematicidal activity with a mortality rate of 87%, 83%, and 80%, respectively, against M. incognita. The VOCs induced severe oxidative stress in nematodes, which caused rapid death. Moreover, in the presence of volatiles, the activity of antioxidant enzymes, i.e., SOD, CAT, POD, and APX, was observed to be enhanced in M. incognita-infested roots, which might reduce the adverse effect of oxidative stress-induced after infection. Moreover, genes responsible for plant growth promotion SlCKX1, SlIAA1, and Exp18 showed an upsurge in expression, while AC01 was downregulated in infested plants. Furthermore, the defense-related genes (PR1, PR5, and SlLOX1) in infested tomato plants were upregulated after treatment with MIV and 2-UD. These findings suggest that GBSC56 possesses excellent biocontrol potential against M. incognita. Furthermore, the study provides new insight into the mechanism by which GBSC56 nematicidal volatiles regulate antioxidant enzymes, the key genes involved in plant growth promotion, and the defense mechanism M. incognita-infested tomato plants use to efficiently manage root-knot disease.

https://www.mdpi.com/1422-0067/22/9/5049/pdf

Nematicidal Volatiles from Bacillus atrophaeus GBSC56 Promote Growth and Stimulate Induced Systemic Resistance in Tomato against Meloidogyne incognita

Essential oils (EOs) are plant-derived volatile and aromatic extracts with diverse biological effects like antibacterial, anti-inflammatory, and antioxidant properties. Recently, consumers' perceptions of synthetic preservatives have grown unfavorable, spurring research in EOs and their application in food preservation and packaging of vegetables, dairy products, fruits, meat products, and other food items. However, the main impediments to using EOs as food preservatives include their safety limitations, distinctive organoleptic effects, and possible contamination by chemical substances like pesticides. This review discusses the recent developments in the application of EOs from plants and spices as antimicrobial agents for food preservation and shelf-life augmentation. We have also highlighted new developments in encapsulating strategies to get beyond some significant intrinsic constraints, such as low water solubility, volatility, bioavailability, and stability in food systems. Lastly, we have also shed light on the recent pioneering in smart packaging systems to prolong the shelf-life of the food product. EOs have the potential to preserve food matrices from various microbes and maintain the quality of meat, fish, dairy, fruits, and vegetable products. They have also proven to greatly influence cooking and increase the shelf life of food products. The core material of encapsulated and nano-encapsulated EOs promise to ensure their continuous release in response to various triggers and promote better food preservation. Overall, this article provides current knowledge about the EOs in food preservation and identifies research avenues that can facilitate the implementation of EOs as natural preservatives in foods. 

Recent trends in the application of essential oils: The next generation of food preservation and food packaging

In this study, we evaluated the effects of volatile organic compounds (VOCs) produced by Bacillus subtilis CF-3 in inhibiting Monilinia fructicola in vitro and in vivo. In the in vitro experiments, the effect of VOCs on the growth of the pathogenic fungi was explored by using plate enthalpy test; mycelial morphology was studied by scanning electron and transmission electron microscopy; and fatty acid contents in the cell membrane were assessed by gas chromatography-mass spectrometry (GC-MS). The results indicated that treatment with benzothiazole and CF-3 for 24 h, in the form of a fermentation broth (24hFB), significantly inhibited the germination of fungal spores, modified hyphal and cell morphology, and decreased the cell membrane fluidity and integrity. In the in vivo experiments, the effect of VOCs on the defense mechanism of peach fruit toward M. fructicola was studied, and we found that benzothiazole and CF-3 24hFB inhibited the activity of the pathogenic enzymes (pectinase, cellulase) secreted by M. fructicola to reduce the decomposition of plant tissues, activate the antioxidant enzymes (peroxidase, polyphenol oxidase, catalase, and superoxide dismutase) in the fruit to eliminate excessive reactive oxygen species in order to reduce plant cell damage, and trigger the disease-resistant enzymes (phenylalanine ammonia-lyase, chitinases, and β-1,3-glucanase) to enhance the resistance of peach fruit to M. fructicola and inhibit its growth. This study suggests that CF-3 VOCs could activate disease-resistant enzymes to prevent the invasion of pathogenic fungi and induce resistance in peach, thereby providing a theoretical basis for future applications.

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Bacillus subtilis CF-3 Volatile Organic Compounds Inhibit Monilinia fructicola Growth in Peach Fruit.

In this study, we investigated the effects of volatile organic compounds (VOCs) produced by Bacillus subtilis CF-3 on the growth and development of Colletotrichum gloeosporioides and evaluated the elicitation of active defense responses in harvested litchi fruits. In vitro experiments were conducted to explore the bacteriostatic effect of VOCs in inhibiting pathogenic fungi by means of plate enthalpy test, scanning electron microscopy, transmission electron microscopy, and gas chromatography–mass spectrometry (GC–MS). The results showed that 2,4-di-tert-butylphenol and CF-3 24-h fermentation broth (24hFB) can significantly inhibit the germination of fungal spores, disrupt hyphal and cell morphology, and decrease cell membrane fluidity and integrity, resulting in the changes of indexes. In addition, the bacteriostasis of VOCs in the defensive ability of litchi fruits to C. gloeosporioides was studied, and it was shown that 2,4-di-tert-butylphenol and CF-3 24hFB can inhibit the activity of the pathogenic enzymes (pectinase and cellulase) secreted by C. gloeosporioides to reduce the decomposition of plant tissues, activate antioxidant enzymes (peroxidase, polyphenol oxidase, catalase, and superoxide dismutase) in the fruit to eliminate excessive reactive oxygen species in fruits in order to reduce plant cell damage and activate disease resistance enzymes (phenylalanineammonialyase, chitinases, β-1,3-glucanase) to enhance the resistance of litchi fruits to C. gloeosporioides and inhibit its growth. This study investigated the bacteriostasis of VOCs in inhibiting C. gloeosporioides and inducing the resistance of litchi fruits, providing a theoretical basis for future applications.

/pdf/volatile-organic-compounds-vocs-from-bacillus-subtilis-cf-3-2zv2ck0mjk.pdf

Volatile organic compounds (VOCs) from Bacillus subtilis CF-3 reduce anthracnose and elicit active defense responses in harvested litchi fruits

Oregano essential oil (OEO) is an effective natural antibacterial agent, but its antibacterial activity against Vibrio vulnificus has not been widely studied. The aim of this study was to investigate the inhibitory effect and germicidal activity of OEO on V. vulnificus and its possible inhibition mechanism. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of OEO against four V. vulnificus strains (ATCC 27562 and three isolates from seafoods) were from 0.06 to 0.15 μL/mL. Compared with untreated bacteria, OEO reduced the concentration of intracellular adenosine triphosphate (ATP), hyperpolarized the cell membrane, increased the level of reactive oxygen species (ROS), and increased the concentration of intracellular malondialdehyde (MDA), but there was no obvious DNA damage at the OEO test concentration. It was indicated that OEO inactivated V. vulnificus by generating ROS which caused lipid peroxidation of cell membranes, thereby reducing the permeability and integrity of cell membranes and causing morphological changes to cells, but there was no obvious damage to DNA. In addition, OEO could effectively kill V. vulnificus in oysters at 25 °C, and the number of bacteria decreased by 48.2% after 0.09% OEO treatment for 10 h. The good inhibitory effect and bactericidal activity of OEO showed in this study, and the economy and security of OEO make it possible to apply OEO to control V. vulnificus contamination in oysters and other seafoods.

/pdf/antibacterial-effect-of-oregano-essential-oil-against-vibrio-14esotul.pdf

Antibacterial Effect of Oregano Essential Oil against Vibrio vulnificus and Its Mechanism

Transcriptomic analysis of the effects of γ-aminobutyric acid treatment on browning and induced disease resistance in fresh-cut apples

Bacillus subtilis is commonly used as a biocontrol bacterium owing to its strong antifungal activity, broad-spectrum inhibition, and general safety. In this study, the inhibitory effects of volatile organic compounds (VOCs) produced by B. subtilis CF-3 on Colletotrichum gloeosporioides, a major destructive phytopathogen of litchi anthracnose, were analyzed using proteomics and transcriptomics. Differentially expressed genes (DEGs) and proteins (DEPs) indicated that the inhibition of C. gloeosporioides by B. subtilis CF-3 VOCs downregulated the expression of genes related to cell membrane fluidity, cell wall integrity, energy metabolism, and production of cell wall-degrading enzymes. Particularly, those important DEGs and DEPs related to the ergosterol biosynthetic and biosynthesis of unsaturated fatty acids are most significantly influenced. 2,4-di-tert-butylphenol, a characteristic component of B. subtilis CF-3 VOCs, also showed a similar effect on C. gloeosporioides. Our results provide a theoretical basis for the potential application of B. subtilis CF-3 in the postharvest protection of fruits and vegetables.

Antifungal Mechanism of Volatile Organic Compounds Produced by Bacillus subtilis CF-3 on Colletotrichum gloeosporioides Assessed Using Omics Technology.

Pengyu Zhao

Papers

Bacillus subtilis CF-3 Volatile Organic Compounds Inhibit Monilinia fructicola Growth in Peach Fruit.

Volatile organic compounds (VOCs) from Bacillus subtilis CF-3 reduce anthracnose and elicit active defense responses in harvested litchi fruits

Antibacterial Effect of Oregano Essential Oil against Vibrio vulnificus and Its Mechanism

Transcriptomic analysis of the effects of γ-aminobutyric acid treatment on browning and induced disease resistance in fresh-cut apples

Antifungal Mechanism of Volatile Organic Compounds Produced by Bacillus subtilis CF-3 on Colletotrichum gloeosporioides Assessed Using Omics Technology.