Microbial Volatile Organic Compounds Research Articles

Comparative profiling of microbial communities and volatile organic compounds in fermented wrapper, binder, and filler cigar tobaccos

BackgroundEconomic benefits for tobacco growers are closely linked to the quality of fermented cigar tobacco leaves (CTLs). This research focused on an in-depth examination of the microbial community and flavor compounds within CTLs, specifically analyzing the wrapper, binder, and filler components of a cigar. The primary objective was to unravel the complex relationship between the microbial composition and the resultant flavor profiles, thereby providing insights that could enhance the economic value of CTLs.ResultsThe study revealed distinct variations in flavor chemicals and microbiota across different sections of CTLs. Prominent species identified in the fermented CTLs included Corynebacterium, Pseudomonas, Staphylococcus, Aspergillus, and Cladosporium. Bidirectional orthogonal partial least squares (O2PLS) analysis pinpointed five bacterial and four fungal species as key contributors to flavor compound formation. Additionally, an analysis considering Within-module and Among-module connectivity highlighted two bacterial and thirteen fungal genera as keystone species. The insights from Partial Least Squares Structural Equation Modeling (PLS-SEM) further underscored the influential role of fungal microorganisms in defining CTLs' flavor profile.ConclusionsThe research findings illuminate the intricate interplay between flavor chemicals and microbes in the traditional fermentation process of CTLs.Graphical

Demonstrating the Applicability of Proton Transfer Reaction Mass Spectrometry to Quantify Volatiles Emitted by the Mycoparasitic Fungus Trichoderma atroviride in Real Time: Monitoring of Trichoderma-Based Biopesticides.

The present study aims to explore the potential application of proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) for real-time monitoring of microbial volatile organic compounds (MVOCs). This investigation can be broadly divided into two parts. First, a selection of 14 MVOCs was made based on previous research that characterized the MVOC emissions of Trichoderma atroviride, which is a filamentous fungus widely used as a biocontrol agent. The analysis of gas-phase standards using PTR-ToF-MS allowed for the categorization of these 14 MVOCs into two groups: the first group primarily undergoes nondissociative proton transfer, resulting in the formation of protonated parent ions, while the second group mainly undergoes dissociative proton transfer, leading to the formation of fragment ions. In the second part of this investigation, the emission of MVOCs from samples of T. atroviride was continuously monitored over a period of five days using PTR-ToF-MS. This also included the first quantitative online analysis of 6-amyl-α-pyrone (6-PP), a key MVOC emitted by T. atroviride. The 6-PP emissions of T. atroviride cultures were characterized by a gradual increase over the first two days of cultivation, reaching a plateau-like maximum with volume mixing ratios exceeding 600 ppbv on days three and four. This was followed by a marked decrease, where the 6-PP volume mixing ratios plummeted to below 50 ppbv on day five. This observed sudden decrease in 6-PP emissions coincided with the start of sporulation of the T. atroviride cultures as well as increasing intensities of product ions associated with 1-octen-3-ol and 3-octanone, whereas both these MVOCs were previously associated with sporulation in T. atroviride. The study also presents the observations and discussion of further MVOC emissions from the T. atroviride samples and concludes with a critical assessment of the possible applications and limitations of PTR-ToF-MS for the online monitoring of MVOCs from biological samples in real time.

Antipathogenic Activities of Volatile Organic Compounds Produced by Bacillus velezensis LT1 against Sclerotium rolfsii LC1, the Pathogen of Southern Blight in Coptis chinensis.

This study explores the antipathogenic properties of volatile organic compounds (VOCs) produced by Bacillus velezensis LT1, isolated from the rhizosphere soil of Coptis chinensis. The impact of these VOCs on the mycelial growth of Sclerotium rolfsii LC1, the causative agent of southern blight in C. chinensis, was evaluated using a double Petri-dish assay. The biocontrol efficacy of these VOCs was further assessed through leaf inoculation and pot experiments. Antifungal VOCs were collected using headspace solid-phase microextraction (SPME), and their components were identified via gas chromatography-mass spectrometry (GC-MS). The results revealed that the VOCs significantly inhibited the mycelial growth and sclerotia germination of S. rolfsii LC1 and disrupted the morphological integrity of fungal mycelia. Under the influence of these VOCs, genes associated with chitin synthesis were upregulated, while those related to cell wall degrading enzymes were downregulated. Notably, 2-dodecanone and 2-undecanone exhibited inhibition rates of 81.67% and 80.08%, respectively. This research provides a novel approach for the prevention and management of southern blight in C. chinensis, highlighting the potential of microbial VOCs in biocontrol strategies.

Evolution of microbial community and the volatilome of fresh-cut chili pepper during storage under different temperature conditions: Correlation of microbiota and volatile organic compounds

The effect of temperature conditions on the evolution of microbial communities and volatile organic compounds (VOCs) in fresh-cut chili peppers during storage was investigated. Results showed that Proteobacteria and Actinobacteriota were the dominant phyla in fresh-cut chili peppers. During storage, bacterial communities changed more dramatically than fungi. Different temperature conditions significantly affected the shift of bacteria at the genus level. At the beginning of storage, Rhodococcus, Pantoea, and Pseudomonas dominated the bacteria. However, on day 8, Pantoea and Enterobacter became the predominant genera at 5 °C and high temperatures (10, 15 °C, dynamic temperature), respectively. No significant variability in bacterial species was observed between different batches. Additionally, 140 VOCs were determined in fresh-cut chili peppers. Twenty-two VOCs were screened and could be recommended as potential spoilage markers. Based on Spearman's correlation analysis results, Enterobacter and Enterococcus were the most positive microorganisms correlated with spoilage markers.

Novel Pseudomonas Species Prevent the Growth of the Phytopathogenic Fungus Aspergillus flavus.

In response to the escalating demand for sustainable agricultural methodologies, the utilization of microbial volatile organic compounds (VOCs) as antagonists against phytopathogens has emerged as a viable eco-friendly alternative. Microbial volatiles exhibit rapid diffusion rates, facilitating prompt chemical interactions. Moreover, microorganisms possess the capacity to emit volatiles constitutively, as well as in response to biological interactions and environmental stimuli. In addition to volatile compounds, these bacteria demonstrate the ability to produce soluble metabolites with antifungal properties, such as APE Vf, pyoverdin, and fragin. In this study, we identified two Pseudomonas strains (BJa3 and MCal1) capable of inhibiting the in vitro mycelial growth of the phytopathogenic fungus Aspergillus flavus, which serves as the causal agent of diseases in sugarcane and maize. Utilizing GC/MS analysis, we detected 47 distinct VOCs which were produced by these bacterial strains. Notably, certain volatile compounds, including 1-heptoxydecane and tridecan-2-one, emerged as primary candidates for inhibiting fungal growth. These compounds belong to essential chemical classes previously documented for their antifungal activity, while others represent novel molecules. Furthermore, examination via confocal microscopy unveiled significant morphological alterations, particularly in the cell wall, of mycelia exposed to VOCs emitted by both Pseudomonas species. These findings underscore the potential of the identified BJa3 and MCal1 Pseudomonas strains as promising agents for fungal biocontrol in agricultural crops.

MOF-derived Co3O4-ZnO heterostructure for 3-methyl-1-butanol detection

Microbial volatile organic compounds (MVOCs) detection with a fast response and high selectivity is barely studied. The challenge is developing a material that matches these factors in different sensing conditions, such as operating temperature and humidity. In this study, we searched for a better way to improve the gas sensing properties of cobalt oxide (Co3O4), synthesizing a MOF-derived (ZIF-67-ZIF-8) p-n heterojunction of Co3O4-ZnO and varying the molar concentrations of these metals. The Co3O4 was synthesized through a mixture of cobalt(II) nitrate hexahydrate and 2-methylimidazole in a simple process at room temperature, forming the ZIF-67, which was then calcinated. The Co3O4-ZnO and ZnO-Co3O4 heterostructures were synthesized by adding zinc(II) nitrate hexahydrate to produce ZIF-8 and create a heterojunction with ZIF-67, followed by calcination. The Co3O4-ZnO sample exhibited higher sensing performance than pure Co3O4 and the heterostructure ZnO-Co3O4. In this case, Co3O4-ZnO exhibited a higher response of 14.6 to 3-methyl-1-butanol (3M1B) with a selectivity ratio of 2.79. These findings could improve food control by monitoring the MVOCs produced by bacteria, such as Pseudomonas spp, in the spoilage process of shrimp. Furthermore, under 65% of relative humidity, this sensor demonstrated a response of 10.4. Therefore, improving the Co3O4 performance as a gas sensor was achievable with a p-n heterojunction of zinc and cobalt, indicating a suitable response under different conditions.

Effects of pretreated garlic on bacterial composition and metabolite profiles during kimchi fermentation

This study investigated the effects of pretreated garlic on the fermentation characteristics of kimchi; four types of kimchi using pretreated garlic [raw (RGK), frozen (FGK), blanched (BGK), and blanched-frozen (BFGK)] were prepared; fermentation was carried out at 4 °C for 6 weeks. The fermentation properties, microbial community composition, metabolic compounds, and volatile organic compounds (VOC) were investigated. The total viable bacterial count in blanched garlic was reduced significantly compared to those in raw and frozen garlic. Latilactobacillus spp. became the dominant species in all kimchi samples as the fermentation progressed. Of the 145 metabolites observed by gas chromatography and mass spectrometry, 51 volatile metabolites were observed. Glucose, fructose, sucrose, lactic acid, citric acid, and mannitol were present as major metabolites (variable importance in projection scores >1.0). Frozen garlic (FGK and BFGK) reduced the production of sulfuric VOC compounds, while raw garlic increased the production of these compounds, specifically that of allyl methyl sulfide, dimethyl disulfide, and dimethyl trisulfide. In conclusion, the condition of garlic added to kimchi affects the abundance of microorganisms during initial fermentation and the quality characteristics of kimchi during the fermentation period. These results help establish garlic pretreatment conditions for kimchi manufacturing.

Signaling pathways involved in microbial indoor air pollutant 3-methyl-1-butanol in the induction of stomatal closure in Arabidopsis.

Indoor air pollution is a global problem and one of the main stress factors that has negative effects on plant and human health. 3-methyl-1-butanol (3MB), an indoor air pollutant, is a microbial volatile organic compound (mVOC) commonly found in damp indoor dwellings. In this study, we reported that 1mg/L of 3MB can elicit a significant reduction in the stomatal aperture ratio in Arabidopsis and tobacco. Our results also showed that 3MB enhances the reactive oxygen species (ROS) production in guard cells of wild-type Arabidopsis after 24h exposure. Further investigation of 24 h 3MB fumigation of rbohD, the1-1, mkk1, mkk3, and nced3 mutants revealed that ROS production, cell wall integrity, MAPK kinases cascade, and phytohormone abscisic acid are all involved in the process of 3MB-induced stomatal. Our findings proposed a mechanism by which 3MB regulates stomatal closure in Arabidopsis. Understanding the mechanisms by which microbial indoor air pollutant induces stomatal closure is critical for modulating the intake of harmful gases from indoor environments into leaves. Investigations into how stomata respond to the indoor mVOC 3MB will shed light on the plant's "self-defense" system responding to indoor air pollution.

Primer Design of Volatile Synthesis Coding Genes in Ralstonia syzygii subsp. celebesensis

Microbes produce various types of volatile organic compounds (VOCs) through metabolism, which can be used for diagnostic purposes. Microbes' types and classes of VOCs are very wide, including fatty acid derivatives (hydrocarbons, alcohols, and ketones), aromatic compounds, nitrogen-containing compounds, and volatile sulfur compounds. Microbial volatile organic compounds (VOCs) can also be divided into several chemical classes: alkenes, alcohols, ketones, benzos, pyrazines, sulfides, acids, esters, and terpenes. This study aimed to design primers for genes encoding volatile synthesis in Ralstonia syzygii subsp. celebesensis, which causes blood disease in the banana plant. Some of the genes involved are adc (acetone synthesis), adhP (ethanol synthesis), ilvA, nirBD (ammonia synthesis), mdcA (propionic acid synthesis), cysI (hydrogen sulfide synthesis), and speBC (putrescine synthesis). Primers were designed and examined for specificity in silico using Primer3Plus, Geneious Prime, and BLAST programs. The numbers of nine pairs designed primers were successfully amplifying the related nine VOC genes of R. syzygii subsp. celebesensis for qPCR.

Correlation between microbial communities and volatile organic compounds in an urban soil provides clues on soil quality towards sustainability of city flowerbeds

Soil functionality is critical to the biosphere as it provides ecosystem services relevant for a healthy planet. The soil microbial composition is significantly impacted by anthropogenic activities, including urbanization. In this context, the study of soil microorganisms associated to urban green spaces has started to be crucial toward sustainable city development. Microbes living in the soil produce and degrade volatile organic compounds (VOCs). The VOC profiles may be used to distinguish between soils with various characteristics and management practices, reflecting variations in the activity of soil microbes that use a variety of metabolic pathways. Here, a combined approach based on DNA metabarcoding and GC-MS analysis was used to evaluate the soil quality from urban flowerbeds in Prato (Tuscany, Italy) in terms of microbial biodiversity and VOC emission profiles, with the final aim of evaluating the possible correlation between composition of microbial community and VOC patterns. Results showed that VOCs in the considered soil originated from anthropic and biological activity, and significant correlations between specific microbial taxa and VOCs were detected. Overall, the study demonstrated the feasibility of the use of microbe-VOC correlation as a proxy for soil quality assessment in urban soils.

Draft genome sequence of a mosquito repellent Bacillus licheniformis strain Ba1 isolated from desert soil.

Microbial volatile organic compounds have been shown to affect a wide insect behavior. In this paper, we report the draft genome sequence of Bacillus licheniformis strain Ba1 previously isolated from desert soil in Morocco. The assembled and annotated draft genome contains 4,726 coding genes, 6 rRNAs and 97 tRNAs.

Biofumigant potential and inhibition mechanism of Trichoderma asperelloides SKRU-01 volatile organic compounds for controlling aflatoxigenic Aspergillus parasiticus and Aspergillus flavus in stored peanuts

Microbial volatile organic compounds (VOCs) have emerged as promising alternatives to synthetic fungicides for managing stored grain. In this study, the inhibitory effects of Trichoderma asperelloides SKRU-01 VOCs on hyphal growth and spore germination of Aspergillus parasiticus TISTR 3276 and A. flavus PSRDC-4 were investigated. The results demonstrated significant suppression of hyphal growth and spore germination in both strains by SKRU-01 VOCs. By using solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS), the SKRU-01 VOCs were identified to contain 23 compounds, with acetophenone being predominant (14.41%). Antifungal experiments revealed that acetophenone, at a minimum inhibitory concentration (MIC) of 1.0 μL/mL (solid media assay) or 1.0 μL/L (vapor phase assay), completely inhibited the growth of both strains. Moreover, the application of SKRU-01 VOCs effectively reduced mold density and aflatoxin B1 (AFB1) production in peanuts and also exhibited superior efficacy compared to acetophenone at a 1/2 MIC concentration. Acetophenone exhibited inhibitory effects on both fungal strains through multiple mechanisms of action. This included its ability to inhibit ergosterol biosynthesis, reduce the aflatoxin inducer methylglyoxal, impair antioxidant defense enzymes, and disrupt non-enzymatic defense molecules. Overall, this research highlights the biofumigant potential of SKRU-01 VOCs in stored grain management and provides novel insights into their antifungal mechanism against A. parasiticus and A. flavus. Furthermore, these findings contribute to the development of sustainable strategies for grain preservation and underscore the broader applications of microbial VOCs in agricultural and food safety practices.

Transcriptomic analysis of Ralstonia solanacearum in response to antibacterial volatiles of Bacillus velezensis FZB42.

Volatile organic compounds (VOCs), produced by a variety of microbial species and used as biological agents, have been demonstrated to play a significant role in controlling phytopathogens. In continuation of our previous studies, we aim to elucidate the underlying mechanisms and pathways involved in interactions between pathogens and microbial VOCs. In the current study, we tested how VOCs produced by Bacillus velezensis FZB42 affect the growth of Ralstonia solanacearum TBBS1 in vitro.Query The result showed that the colony growth of R. solanacearum was reduced with an inhibition rate of 0.83 ± 0.043 as compared to the control 1.7 ± 0.076, respectively. The number of viable cells of R. solanacearum was significantly decreased to 7.68CFU/mL as compared to the control (9.02CFU/mL). In addition, transcriptomic analysis of R. solanacearum in response to VOCs produced by FZB42 was performed to better understand the effect of VOCs on R. solanacearum. The transcriptional response of R. solanacearum to FZB42-VOCs was determined using an Illumina RNA-seq approach. The results revealed significant changes in the expression of 2094 R. solanacearum genes, including 593 upregulated and 1501 downregulated genes. To validate the RNA-seq results, the expression of 10 genes was quantified using RT-qPCR. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used to functionally annotate differentially expressed genes. Significant changes were observed in genes directly or indirectly related to virulence, including those related to bacterial invasion, motility, chemotaxis, and secretion systems. Overall, RNA-seq profiling provides new insights into the possible fundamental molecular mechanisms that are responsible for the reduction in growth and virulence of R. solanacearum upon application of FZB42-VOC.

Dimethylpolysulfides production as the major mechanism behind wheat fungal pathogen biocontrol, by Arthrobacter and Microbacterium actinomycetes.

Volatile organic compounds (VOCs) produced by plant-associated microorganisms could serve as natural biocontrol compounds. In this work, we investigate the potential of wheat rhizosphere Microbacterium and Arthrobacter actinomycetes to inhibit the growth of major wheat phytopathogenic fungi, Fusarium graminearum and Zymoseptoria tritici via production of antifungal VOCs. A correlative analysis between fungal-growth inhibition versus bacterial volatilomic profiles identified four dimethylpolysulfide (DMPS) VOCs as the main active compounds behind their biocontrol potential. Subsequent inhibition assays reveal that DMTriS (dimethyltrisulfide) exhibits the strongest inhibition effects, then dimethyldisulfide (DMDiS). Further investigation focuses on the mechanisms behind F. graminearum-growth inhibition by the most active strain Microbacterium JM188 in dual culture. Surprisingly, nine interaction-induced VOCs, including two fungal sesquiterpenes, were exclusively detected in dual cultures, suggesting a complex interplay between microbial VOC production and sensing. More importantly, all JM188 VOCs, including antifungal DMPS, were less abundant in dual cultures, suggesting an uptake of bacterial VOCs by the fungus. Quantification of pure DMPS after confrontation with F. graminearum confirmed complete and partial uptake by the fungus of DMTriS and DMDiS VOCs, respectively, suggesting a potential link between the fungal uptake level of bacterial VOCs and their toxicity. Finally, we demonstrated that F. graminearum growth inhibition leads to a complete depletion of DON (deoxynivalenol) carcinogenic mycotoxins, highlighting a significant modulation of fungal metabolism. Collectively, these results pinpoint DMPS as broad-range fungal-inhibiting VOCs produced by rhizosphere Microbacterium and Arthrobacter, and emphasize the extensive VOC-mediated interplay between bacterial biocontrol agents and fungal pathogens.IMPORTANCEAs the management of wheat fungal diseases becomes increasingly challenging, the use of bacterial agents with biocontrol potential against the two major wheat phytopathogens, Fusarium graminearum and Zymoseptoria tritici, may prove to be an interesting alternative to conventional pest management. Here, we have shown that dimethylpolysulfide volatiles are ubiquitously and predominantly produced by wheat-associated Microbacterium and Arthrobacter actinomycetes, displaying antifungal activity against both pathogens. By limiting pathogen growth and DON virulence factor production, the use of such DMPS-producing strains as soil biocontrol inoculants could limit the supply of pathogen inocula in soil and plant residues, providing an attractive alternative to dimethyldisulfide fumigant, which has many non-targeted toxicities. Notably, this study demonstrates the importance of bacterial volatile organic compound uptake by inhibited F. graminearum, providing new insights for the study of volatiles-mediated toxicity mechanisms within bacteria-fungus signaling crosstalk.

Determination of blood:air, urine:air and plasma:air partition coefficients of selected microbial volatile organic compounds

Partition coefficients (PCs) are essential parameters for understanding the toxicokinetics of chemicals in the human body since they are used in the description of different processes of absorption, distribution, and excretion in physiologically based pharmacokinetic (PBPK) models used in chemical exposure and risk assessment. The goal of this study was to determine urine:air, blood:air and plasma:air partition coefficients (PCs) of microbial volatile organic compounds (mVOCs) previously selected as having high potential as biomarkers of indoor mold exposure. To achieve this goal, the vial-equilibration technique was used, and quantification was performed using headspace gas chromatography tandem mass spectrometry (HS-GC-MS/MS) analysis. Matrix:air PCs of 19 different mVOCs have been successfully determined and their values ranged between 14 and 3586 for urine:air, 78 and 4721 for blood:air and 64 and 5604 for plasma:air PCs. Water:air PCs were also determined, and their values varied between 16 and 2210, showing a good correlation with urine:air PCs for 17 compounds of the selected mVOCs (R2 = 0.97, slope close to unity) indicating that water:air PCs below 103 may be a good surrogate for urine:air PCs. All studied mVOCs have high blood:air PCs (greater than 78) indicating strong pulmonary uptake. Due to their high blood:urine PCs, some mVOCs may be more easily measured in blood than in urine. This work is an important preliminary step toward the use of mVOCs as potential biomarkers of indoor mold exposure. The data obtained in this study will help to determine the most appropriate matrix to use in this biomonitoring approach and will eventually facilitate the development of PBPK models for these chemicals.

Fungal volatile organic compounds: mechanisms involved in their sensing and dynamic communication with plants.

Microbial volatile organic compounds (MVOCs) are mixtures of gas-phase hydrophobic carbon-based molecules produced by microorganisms such as bacteria and fungi. They can act as airborne signals sensed by plants being crucial players in triggering signaling cascades influencing their secondary metabolism, development, and growth. The role of fungal volatile organic compounds (FVOCs) from beneficial or detrimental species to influence the physiology and priming effect of plants has been well studied. However, the plants mechanisms to discern between FVOCs from friend or foe remains significantly understudied. Under this outlook, we present an overview of the VOCs produced by plant-associate fungal species, with a particular focus on the challenges faced in VOCs research: i) understanding how plants could perceive FVOCs, ii) investigating the differential responses of plants to VOCs from beneficial or detrimental fungal strains, and finally, iii) exploring practical aspects related to the collection of VOCs and their eco-friendly application in agriculture.

Microwave-assisted solvothermal synthesis of In-MIL-68 derived hollow In2O3 microrods for enhanced 1-pentanol sensing performance

The development of microbial volatile organic compounds (MVOCs) sensors is helpful due to the detection of toxic contaminants in foods, non-invasive disease diagnosis, and monitoring of contamination in industrial processes. Materials that are typically applied in the sensors field are semiconductor metal oxides (SMOx) since they have shown efficiency in identifying gases. Using metal-organic frameworks (MOFs) as precursors is an exciting approach to producing well-structured SMOx. Therefore, we report the preparation and characterization of In-MIL-68 (a MOF composed of terephthalic acid) derived hollow In2O3 microrods. The sensor material was obtained by the microwave-assisted solvothermal (MAS) method and subsequent calcination. We also show the application of the hollow In2O3 microrods as a 1-pentanol sensor for the first time. The sensor demonstrated exceptional sensitivity to this MVOC compared to other sensors reported in the literature, achieving a great response of 390 for 100 ppm of this compound at 350 °C.

Advances in microbial analysis: Based on volatile organic compounds of microorganisms in food.

In recent years, microbial volatile organic compounds (mVOCs) produced by microbial metabolism have attracted more and more attention because they can be used to detect food early contamination and flaws. So far, many analytical methods have been reported for the determination of mVOCs in food, but few integrated review articles discussing these methods are published. Consequently, mVOCs as indicators of food microbiological contamination and their generation mechanism including carbohydrate, amino acid, and fatty acid metabolism are introduced. Meanwhile, a detailed summary of the mVOCs sampling methods such as headspace, purge trap, solid phase microextraction, and needle trap is presented, and a systematic and critical review of the analytical methods (ion mobility spectrometry, electronic nose, biosensor, and so on) of mVOCs and their application in the detection of food microbial contamination is highlighted. Finally, the future concepts that can help improve the detection of food mVOCs are prospected.

Biocontrol of fungal phytopathogens by Bacillus pumilus.

Plant growth-promoting bacteria are one of the most interesting methods of controlling fungal phytopathogens. These bacteria can participate in biocontrol via a variety of mechanisms including lipopeptide production, hydrolytic enzymes (e.g., chitinase, cellulases, glucanase) production, microbial volatile organic compounds (mVOCs) production, and induced systemic resistance (ISR) triggering. Among the bacterial genera most frequently studied in this aspect are Bacillus spp. including Bacillus pumilus. Due to the range of biocontrol traits, B. pumilus is one of the most interesting members of Bacillus spp. that can be used in the biocontrol of fungal phytopathogens. So far, a number of B. pumilus strains that exhibit biocontrol properties against fungal phytopathogens have been described, e.g., B. pumilus HR10, PTB180, B. pumilus SS-10.7, B. pumilus MCB-7, B. pumilus INR7, B. pumilus SE52, SE34, SE49, B. pumilus RST25, B. pumilus JK-SX001, and B. pumilus KUDC1732. B. pumilus strains are capable of suppressing phytopathogens such as Arthrobotrys conoides, Fusarium solani, Fusarium oxysporum, Sclerotinia sclerotiorum, Rhizoctonia solani, and Fagopyrum esculentum. Importantly, B. pumilus can promote plant growth regardless of whether it alters the native microbiota or not. However, in order to increase its efficacy, research is still needed to clarify the relationship between the native microbiota and B. pumilus. Despite that, it can already be concluded that B. pumilus strains are good candidates to be environmentally friendly and commercially effective biocontrol agents.

Rapid and Online Detection of Foodborne Bacteria via a Novel Ultraviolet Photoionization Time-of-Flight Mass Spectrometry.

Foodborne bacteria are widespread contaminated sources of food; hence, the real-time monitoring of pathogenic bacteria in food production is important for the food industry. In this study, a novel rapid detection method based on microbial volatile organic compounds (MVOCs) emitted from foodborne bacteria was established by using ultraviolet photoionization time-of-flight mass spectrometry (UVP-TOF-MS). The results showed obvious differences of MVOCs among the five species of bacteria, and the characteristic MVOCs for each bacterium were selected by a feature selection algorithm. Online monitoring of MVOCs during bacterial growth displayed distinct metabolomic patterns of the five species. MVOCs were most abundant and varied among species during the logarithmic phase. Finally, MVOC production by bacteria in different food matrixes was explored. The machine learning models for bacteria cultured in different matrixes showed a good classification performance for the five species with an accuracy of over 0.95. This work based on MVOC analysis by online UVP-TOF-MS achieved effective rapid detection of bacteria and showed its great application potential in the food industry for bacterial monitoring.