Antifungal activity and action mechanisms of 2, 4-Di-tert-butylphenol from Bacillus amyloliquefaciens Z-7 volatile organic compounds against Verticillium dahliae.

Volatile organic compounds (VOCs) are ubiquitous environmental toxicants with pre-clinical evidence of decreased vascular health. Research to date has focused on single VOC metabolites and data is lacking on the effects on human vascular health. Many VOCs are strongly correlated with similar exposure sources. Though the compounding effects are poorly defined, they are likely to increase the overall toxicity. Therefore, we examined single VOC metabolites and mixtures’ association with flow mediated dilation (FMD), an index of vascular health. We recruited adult participants into a CV risk cohort, aged 25-70 years, from 2018 and 2019. A panel of urinary VOC metabolites were measured in 308 non-smoking participants who had completed brachial artery FMD. Regression analysis of 16 VOC analytes was tested for associations with %FMD and models were adjusted for covariates selected a priori including age, sex, diabetes and ACE inhibitors. We examined the joint effect of MU, 3HPMA, CEMA, CYMA, DHBMA, 2HPMA, 2MHA, and AAMA mixtures on log-transformed %FMD using quantile-based g-computation models adjusted for the covariates above and for correlated VOC metabolites that were not associated with FMD in single metabolite analyses. The mean %FMD was 7.1 % ± 4.7%. VOC metabolites that were predictors of decreased %FMD in fully adjusted models were 3HPMA (β=-1.275; 95% CI= -2.402, -0.148; p=0.027), CEMA (β= -1.204; 95% CI= -2.051; -0.357 p=0.006), AAMA (β=-1.125; 95% CI= -2.156, -0.094; p=0.033), 2HPMA (β= -1.035; 95% CI= -1.847, -0.222 p=0.013), and 2MHA (β=-0.623; 95% CI= -1.123, -0.124; p=0.015). Most VOC metabolites had fair to moderate correlations in bivariate analyses (Spearman correlation from 0.06 to 0.60). We found that a quartile increase in the VOC mixture was associated with 20% lower percent FMD (ψ -0.18; 95%CI= -0.35, -0.02; p=0.027) in adjusted models. We found the overall mixture effect was driven primarily by 3HPMA, followed by CYMA, CEMA, 2MHA, and AAMA. Therefore, the main driver of the association between the VOC mixture and decreased vascular function is acrolein and to a lesser extent acrylonitrile. Future research could focus on identifying sources of exposure to these VOCs to promote better vascular health among non-smokers.

Antifungal mechanisms of volatile organic compounds from Streptomyces albidoflavus SC-3 against postharvest kiwifruit rot caused by Botryosphaeria dothidea.

Microbial communities in trickle bed air biofilters (TBABs) were evaluated under conditions of interchanging the feed volatile organic compounds (VOCs) and VOC mixtures. Three independent TBABs (Biofilter “A,” “B,” and “C”) were run under interchanging VOCs conditions with different initial VOCs. Two aromatic compounds (toluene and styrene) and two oxygenated compounds (methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK)) were interchanged as single solutes. Two other TBABs “D” and “E” were run for two VOC mixtures. Biofilter “D” had a VOC mixture with equal molar ratio of the four components and Biofilter “E” received a VOC mixture with its composition based on EPA 2003 emission report. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes was used to assess the microbial richness in TBABs for treating the VOC mixtures and the impact of interchanging VOCs on the bacterial community structure in the biofilters. The results from DGGE indicated that the microbial community structure in the biofilter was different after each interchange of VOCs. Some bands of microbial species faded and some bands were strengthened. For the two TBABs treating VOC mixtures, the microbial species did not show significant difference, but the richness among these species was different from each other.

White-nose syndrome, caused by the psychrophilic fungus Pseudogymnoascus destructans, is a wildlife disease that infects hibernating bats, resulting in the deaths of millions of bats in North America. Previous studies have confirmed that volatile organic compounds (VOCs) effectively inhibit the growth of P. destructans, but the antifungal mechanisms of these compounds have not been comprehensively characterized. This study screened two VOCs, 2,5-dimethylcyclohexanol (DMCH) and nonanal, identified from bat cave environments for their potent in vitro inhibition of P. destructans. Scanning and transmission electron microscopy revealed mycelial deformations and disruptions in cellular structures following treatment with these compounds. Physiological and biochemical assays showed higher Annexin V-fluorescein isothiocyanate/propidium (Annexin V-FITC/PI) signals consistent with mycelial apoptosis, increased reactive oxygen species (ROS) levels, higher adenosine triphosphate (ATP), superoxide anion, and glutathione (GSH) contents, and lower catalase (CAT) and superoxide dismutase (SOD) activities. Integrated transcriptomic and metabolomic analyses of mycelia exposed to DMCH or nonanal indicated disruption of cell wall and membrane integrity, altered expression of virulence-associated genes, and perturbation of primary metabolism and energy homeostasis. We also observed signatures of heightened oxidative stress, overexpression of ribosomal genes, and modulation of the MAPK signaling pathway. This study provides novel insights into the antifungal effects of VOCs targeting P. destructans and offers a scientific basis for combating white-nose syndrome.IMPORTANCEWhite-nose syndrome, driven by the cold-adapted fungus Pseudogymnoascus destructans, has decimated hibernating bat populations across North America, with profound ecological and economic consequences. Although volatile organic compounds (VOCs) have emerged as promising antifungal agents, their modes of action against P. destructans remain poorly defined. In this study, we demonstrate that two cave-derived VOCs, 2,5-dimethylcyclohexanol (DMCH) and nonanal, not only deform fungal ultrastructure and trigger apoptosis, but also induce severe oxidative stress, disrupt energy metabolism, and dysregulate critical signaling pathways. By integrating transcriptomic and metabolomic profiling, we elucidate how DMCH and nonanal exposure compromises cell wall and membrane integrity, alters virulence gene expression, and perturbs the MAPK cascade, culminating in fungal cell death. These findings advance our mechanistic understanding of VOCs antifungal activity and highlight a novel, environmentally inspired strategy for mitigating white-nose syndrome. Moreover, our work lays the groundwork for the development of VOC-based interventions to protect vulnerable bat populations and preserve ecosystem health.

Verticillium dahliae is one of the most destructive fungal pathogens, causing substantial economic losses in agriculture and forestry. The use of plant growth-promoting rhizobacteria (PGPR) is an effective and environmentally friendly strategy for controlling diseases caused by V. dahliae. In this study, 90 mm in diameter Petri plates were used to test the effect of volatile organic compounds (VOCs) produced by different concentrations of Pseudomonasaurantiaca ST-TJ4 cells suspension on V. dahliae mycelia radial growth and biomass. The mycelial morphology was observed by using scanning electron microscopy. The conidia germination and microsclerotia formation of V. dahliae were evaluated. The VOCs with antifungal activity were collected by headspace solid-phase microextraction (SPME), and their components were analyzed by gas chromatography-mass spectrometry (GC-MS). The VOCs produced by strain ST-TJ4 significantly inhibited the growth of mycelium of V. dahliae. The morphology of the hyphae was rough and wrinkled when exposed to VOCs. The VOCs of strain ST-TJ4 have a significant inhibitory effect on V. dahliae conidia germination and microsclerotia formation. At the same time, the VOCs also reduce the expression of genes related to melanin synthesis in V. dahliae. In particular, the expression of the hydrophobin gene (VDAG-02273) was down-regulated the most, about 67-fold. The VOCs effectively alleviate the severity of cotton root disease. In the volatile profile of strain ST-TJ4, 2-undecanone and 1-nonanol assayed in the range 10–200 µL per plate revealed a significant inhibitory effect on V. dahliae mycelial radial growth. These compounds may be useful to devise new control strategies for control of Verticillium wilt disease caused by V. dahliae.

Verticillium wilt (VW) of potato is mainly caused by two species of fungal pathogens called Verticillium dahliae and Verticillium albo-atrum (Johnson et al. 2010). V. dahliae is a broad-host range pathogen that severely affects potato production. In a recent study, three pathogenic races (1, 2, and 3) of V. dahliae infecting lettuce from coastal California were identified based on the presence of three distinct effectors: Ave1, VdR2e, and VdR3e (Mandal et al. 2024). Potato plants with VW symptoms, including foliar chlorosis, flagging, and vascular discoloration, were observed in July and August of 2022 and 2023 on more than 80% of potato plants grown in a naturally infested experimental disease nursery farm in Sherburne County, Minnesota (45°20'18.0"N 93°49'41.2"W), a major potato growing county. In July 2023, multiple stem samples were collected and surface sterilized. After 5-7 days of growth on water agar, 12 colonies exhibiting microsclerotia and verticillate phialides were selected. The phialides were arranged in (1-)2-3(-8) whorls below the transverse septum and (1-)2-4(-6) whorls near the apex (Inderbitzin et al. 2011). Following genomic DNA isolation, species were verified through PCR amplification and sequencing of the internal transcribed spacer regions using ITS1/ITS4 and DF/DR Vd.ITS primers (Gardes et al. 1993; Inderbitzin et al. 2013) (Genbank accession no.: ITS1/4: PQ644054, PQ644303, PQ644449, PQ644509, PQ644510, PQ644586, PQ665302, PQ644587, PQ644605, PQ665303, PQ644606, PQ644629; DF/DR Vd.ITS: PQ644632, PQ644634, PQ644896, PQ644897, PQ644903, PQ644902, PQ644907, PQ644906, PQ645019, PQ665304, PQ645052, PQ645073, PQ662628, PQ662629). BLAST searches resulted in 99% sequence identity with V. dahliae. Isolate PN15.23 (ITS1/4: PQ644587, DF/DR: PQ644906) used for potato infection study, shared the highest nucleotide identity (99%, 531/536 bp, 99.57%, 458/460 bp) with V. dahliae isolated from Aribdopsis arenosa (ON193840). Race typing of isolates was conducted using race-specific effector primers for Ave1 (race 1), VdR2e (race 2), and VdR3e (race 3), with known isolates Ls16, Ls4325, and Ca4317 as PCR positive controls (Mandal et al. 2024). Amplification and sequencing of VdR3e confirmed the presence of V. dahliae race 3 (PQ662628 and PQ662629) with 99.37% (111/114 amino acid) protein sequence similarity (BLASTX) to PNH37750. To fulfill Koch's postulates, the PN15.23 isolate was used to infect five, six week old Umatilla potato plants grown in Sungro soil germination mix by inoculating the soil near the root zone with V. dahliae conidia (10 ml of 2x106 cells/ml). Plants were maintained in greenhouse conditions at 22.5°C, with a 16/8 light/dark photoperiod and 65% relative humidity. Three weeks post-infection, watering frequency was reduced to 33% to exacerbate infection symptoms. Infected plants displayed typical VW symptoms, while control plants had no visible VW symptoms. Re-isolation based on apparent morphology was successful from four out of five infected plants. These four had identical V. dahliae ITS1/4 and DF/DR sequences to PN15.23. No growth was observed in five controls. To our knowledge, this is the first report of race 3 V. dahliae causing VW in Minnesota or in potato, highlighting the potential for continued yield losses until resistant cultivars for all three races are identified or developed. These findings are crucial for plant pathologists and breeders developing disease management strategies.

Four classes of plant growth regulators were tested for their effects on Verticillium wilt (Verticillium dahliae) of potato (Solanum tuberosum L.). These substances had auxin, cytokinin, gibberellin, or growth retardant activity. Preliminary greenhouse experiments were conducted to screen materials for effectiveness and to determine suitable application rates. A series of field experiments was then conducted over a four year period. The auxin, napthalene acetic acid, consistently reduced wilt and stem colonization byV. dahliae both in the field and in the greenhouse. Indole acetic acid was only partially effective at reducing wilt and stem colonization, possibly due to its labile nature. Other growth regulators, benzyladenine, (a cytokinin), gibberellic acid — A3 (a gibberellin), chlorflurenol and daminozide (growth retardants), either had no consistent effect or increased wilt and stem colonization. The effect of auxins on wilt reduction was observed in the highly susceptible cultivar Norgold Russet, the moderately susceptible Russet Burbank, and the highly resistant selection A66107-51. Although napthalene acetic acid significantly reduced wilt severity (up to 50%) in field grown Russet Burbank, the reductions in stem colonization byV. dahliae were not of the same magnitude as seen when comparing the highly resistant selection A66107-51 with a susceptible clone. Growth regulator treatments that suppressed wilt or stem colonization did not increase total yield and generally resulted in tuber malformations.

We report on novel microcantilever heater sensors with separate AlGaN/GaN heterostructure based heater and sensor channels to perform advanced volatile organic compound (VOC) detection and mixture analysis. Operating without any surface functionalization or treatment, these microcantilevers utilize the strong surface polarization of AlGaN, as well as the unique heater and sensor channel geometries, to perform selective detection of analytes based on their latent heat of evaporation and molecular dipole moment over a wide concentration range with sub-ppm detection limit. The dual-channel microcantilevers have demonstrated much superior sensing behavior compared to the single-channel ones, with the capability to not only identify individual VOCs with much higher specificity, but also uniquely detect them in a generic multi-component mixture of VOCs. In addition, utilizing two different dual channel configurations and sensing modalities, we have been able to quantitatively determine individual analyte concentration in a VOC mixture. An algorithm for complete mixture analysis, with unique identification of components and accurate determination of their concentration, has been presented based on simultaneous operation of an array of these microcantilever heaters in multiple sensing modalities.

Removal of binary and ternary synergistic mixtures of ozone and VOCs by activated carbon filter: Mathematical modelling

Difference of photodegradation characteristics between single and mixed VOC pollutants under simulated sunlight irradiation

Abatement of mixture of volatile organic compounds (VOCs) in a catalytic non-thermal plasma reactor

Vanillin and its derivatives, potential promising antifungal agents, inhibit Aspergillus flavus spores via destroying the integrity of cell membrane rather than cell wall

Our previous study showed that cinnamaldehyde (CA) significantly inhibited the mycelial growth of Geotrichum citri-aurantii, one of the main postharvest pathogens in citrus fruits. This study investigated the antifungal mechanism of CA against G. citri-aurantii. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that CA treatment led to clear morphological changes in the cell walls and membranes of G. citri-aurantii. However, the membrane integrity, total lipids and ergosterol contents were not apparently affected by CA treatment. Notably, the extracellular alkaline phosphatase (AKP) activity was increased after CA treatment, suggesting impairment in cell wall permeability. A weakened fluorescence in the cell wall, a decrease in the chitin contents, and changes of ten genes involved in cell wall integrity were also observed. These results suggested that CA may exhibit its antifungal activity against G. citri-aurantii by interfering the build of cell wall and therefore lead to the damage of cell wall permeability and integrity.

This study examines the primary and secondary products resulting from reactions initiated by adding ozone to complex mixtures of volatile organic compounds (VOC). The mixtures were representative of organic species typically found indoors, but the concentrations tended to be higher than normal indoor levels. Each 4-h experiment was conducted in a controlled environmental facility (CEF, 25 m3) ventilated at approximately 1.8 h(-1). The mixture investigated included 23 VOC (no O3), O3/23 VOC, O3/21 VOC (no d-limonene or alpha-pinene), and O3/terpene only (d-limonene and alpha-pinene). The net O3 concentration was approximately 40 ppb in each experiment, and the total organic concentration was 26 mg/m3 for the 23 VOC mixture, 25 mg/m3 for the 21 VOC mixture, and 1.7 mg/m3 for the d-limonene and alpha-pinene mixture. When the 23 VOC were added to the CEF containing no O3, no compounds other than those deliberately introduced were observed. When O3 was added to the CEF containing the 23 VOC mixture, both gas and condensed phase products were found, including aldehydes, organic acids, and submicron particles (140 microg/m3). When O3 was added to the CEF containing the 21 VOC without the two terpenes (O3/21 VOC condition), most of the products that were observed in the O3/23 VOC experiments were no longer present or present at much lower concentrations. Furthermore, the particle mass concentration was 2-7 microg/m3, indistinguishable from the background particle concentration level. When O3 was added to the CEF containing only two terpenes, the results were similar to those in the O3/23 VOC experiments, but the particle mass concentration (190 microg/m3) was higher. The results indicate that (i) O3 reacts with unsaturated alkenes under indoor conditions to generate submicron particles and other potentially irritating species, such as aldehydes and organic acids; (ii) the major chemical transformations that occurred under our experimental conditions were driven by O3/d-limonene and O3/alpha-pinene reactions; and (iii) the hydroxyl radicals (OH) that were generated from the O3/terpene reactions played an important role in the chemical transformations and were responsible for approximately 56-70% of the formaldehyde, almost all of the p-tolualdehyde, and 19-29% of the particle mass generated in these experiments.

In disease-suppressive soils, plants are protected from infections by specific root pathogens due to the antagonistic activities of soil and rhizosphere microorganisms. For most disease-suppressive soils, however, the microorganisms and mechanisms involved in pathogen control are largely unknown. Our recent studies identified Actinobacteria as the most dynamic phylum in a soil suppressive to the fungal root pathogen Rhizoctonia solani. Here we isolated and characterized 300 isolates of rhizospheric Actinobacteria from the Rhizoctonia-suppressive soil. Streptomyces species were the most abundant, representing approximately 70% of the isolates. Streptomyces are renowned for the production of an exceptionally large number of secondary metabolites, including volatile organic compounds (VOCs). VOC profiling of 12 representative Streptomyces isolates by SPME-GC-MS allowed a more refined phylogenetic delineation of the Streptomyces isolates than the sequencing of 16S rRNA and the house-keeping genes atpD and recA only. VOCs of several Streptomyces isolates inhibited hyphal growth of R. solani and significantly enhanced plant shoot and root biomass. Coupling of Streptomyces VOC profiles with their effects on fungal growth, pointed to VOCs potentially involved in antifungal activity. Subsequent assays with five synthetic analogs of the identified VOCs showed that methyl 2-methylpentanoate, 1,3,5-trichloro-2-methoxy benzene and the VOCs mixture have antifungal activity. In conclusion, our results point to a potential role of VOC-producing Streptomyces in disease suppressive soils and show that VOC profiling of rhizospheric Streptomyces can be used as a complementary identification tool to construct strain-specific metabolic signatures.