Quorum sensing gene regulation in Staphylococcus epidermidis reduces the attraction of Aedes aegypti (L.) (Diptera: Culicidae)

Introduction

Identifying mechanisms regulating mosquito attraction to hosts is key to suppressing pathogen transmission. Historically, the ecology of the host microbial community and its influence on mosquito attraction, specifically, whether bacterial communication through quorum sensing (QS) modulates VOC production that affects mosquito behavior have not been extensively considered.

Methods

Behavioral choice assays were applied along with volatile collection, followed by GC-MS and RNA transcriptome analyses of bacteria with and without a quorum-sensing inhibitor, furanone C-30.

Results

Utilizing the quorum-sensing inhibitor on a skin-inhabiting bacterium, Staphylococcus epidermidis, we disrupted its interkingdom communication with adult Aedes aegypti and mitigated their attraction to a blood-meal by 55.1%.

Discussion

One potential mechanism suppressing mosquito attraction could be the reduction (31.6% in our study) of bacterial volatiles and their associated concentrations by shifting S. epidermidis metabolic (12 of 29 up regulated genes) and stress (5 of 36 down regulated genes) responses. Manipulating the quorum-sensing pathways could serve as a mechanism to reduce mosquito attraction to a host. Such manipulations could be developed into novel control methods for pathogen-transmitting mosquitoes and other arthropods.

Bacterial volatile organic compounds (VOCs) promote growth and induce metabolic changes in rice

Plant growth-promoting bacteria (PGPB) represent an eco-friendly alternative to reduce the use of chemical products while increasing the productivity of economically important crops. The emission of small gaseous signaling molecules from PGPB named volatile organic compounds (VOCs) has emerged as a promising biotechnological tool to promote biomass accumulation in model plants (especially Arabidopsis thaliana) and a few crops, such as tomato, lettuce, and cucumber. Rice (Oryza sativa) is the most essential food crop for more than half of the world's population. However, the use of VOCs to improve this crop performance has not yet been investigated. Here, we evaluated the composition and effects of bacterial VOCs on the growth and metabolism of rice. First, we selected bacterial isolates (IAT P4F9 and E.1b) that increased rice dry shoot biomass by up to 83% in co-cultivation assays performed with different durations of time (7 and 12 days). Metabolic profiles of the plants co-cultivated with these isolates and controls (without bacteria and non-promoter bacteria-1003-S-C1) were investigated via ¹H nuclear magnetic resonance. The analysis identified metabolites (e.g., amino acids, sugars, and others) with differential abundance between treatments that might play a role in metabolic pathways, such as protein synthesis, signaling, photosynthesis, energy metabolism, and nitrogen assimilation, involved in rice growth promotion. Interestingly, VOCs from IAT P4F9 displayed a more consistent promotion activity and were also able to increase rice dry shoot biomass in vivo. Molecular identification by sequencing the 16S rRNA gene of the isolates IAT P4F9 and E.1b showed a higher identity with Serratia and Achromobacter species, respectively. Lastly, volatilomes of these and two other non-promoter bacteria (1003-S-C1 and Escherichia coli DH5α) were evaluated through headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. Compounds belonging to different chemical classes, such as benzenoids, ketones, alcohols, sulfide, alkanes, and pyrazines, were identified. One of these VOCs, nonan-2-one, was validated in vitro as a bioactive compound capable of promoting rice growth. Although further analyses are necessary to properly elucidate the molecular mechanisms, our results suggest that these two bacterial isolates are potential candidates as sources for bioproducts, contributing to a more sustainable agriculture.

The power of the smallest: The inhibitory activity of microbial volatile organic compounds against phytopathogens

Plant diseases caused by phytopathogens result in huge economic losses in agriculture. In addition, the use of chemical products to control such diseases causes many problems to the environment and to human health. However, some bacteria and fungi have a mutualistic relationship with plants in nature, mainly exchanging nutrients and protection. Thus, exploring those beneficial microorganisms has been an interesting and promising alternative for mitigating the use of agrochemicals and, consequently, achieving a more sustainable agriculture. Microorganisms are able to produce and excrete several metabolites, but volatile organic compounds (VOCs) have huge biotechnology potential. Microbial VOCs are small molecules from different chemical classes, such as alkenes, alcohols, ketones, organic acids, terpenes, benzenoids and pyrazines. Interestingly, volatilomes are species-specific and also change according to microbial growth conditions. The interaction of VOCs with other organisms, such as plants, insects, and other bacteria and fungi, can cause a wide range of effects. In this review, we show that a large variety of plant pathogens are inhibited by microbial VOCs with a focus on the in vitro and in vivo inhibition of phytopathogens of greater scientific and economic importance in agriculture, such as Ralstonia solanacearum, Botrytis cinerea, Xanthomonas and Fusarium species. In this scenario, some genera of VOC-producing microorganisms stand out as antagonists, including Bacillus, Pseudomonas, Serratia and Streptomyces. We also highlight the known molecular and physiological mechanisms by which VOCs inhibit the growth of phytopathogens. Microbial VOCs can provoke many changes in these microorganisms, such as vacuolization, fungal hyphal rupture, loss of intracellular components, regulation of metabolism and pathogenicity genes, plus the expression of proteins important in the host response. Furthermore, we demonstrate that there are aspects to investigate by discussing questions that are still not very clear in this research area, especially those that are essential for the future use of such beneficial microorganisms as biocontrol products in field crops. Therefore, we bring to light the great biotechnological potential of VOCs to help make agriculture more sustainable.

Microbial Volatile Organic Compounds: An Alternative for Chemical Fertilizers in Sustainable Agriculture Development

Microorganisms are exceptional at producing several volatile substances called microbial volatile organic compounds (mVOCs). The mVOCs allow the microorganism to communicate with other organisms via both inter and intracellular signaling pathways. Recent investigation has revealed that mVOCs are chemically very diverse and play vital roles in plant interactions and microbial communication. The mVOCs can also modify the plant's physiological and hormonal pathways to augment plant growth and production. Moreover, mVOCs have been affirmed for effective alleviation of stresses, and also act as an elicitor of plant immunity. Thus, mVOCs act as an effective alternative to various chemical fertilizers and pesticides. The present review summarizes the recent findings about mVOCs and their roles in inter and intra-kingdoms interactions. Prospects for improving soil fertility, food safety, and security are affirmed for mVOCs application for sustainable agriculture.

Henry's Law Constants and Indoor Partitioning of Microbial Volatile Organic Compounds

Microbial volatile organic compounds (MVOCs) play an essential role in many environmental fields, such as indoor air quality. Long-term exposure to odorous and toxic MVOCs can negatively affect the health of occupants. Recently, the involvement of surface reservoirs in indoor chemistry has been realized, which signifies the importance of the phase partitioning of volatile organic pollutants. However, reliable partition coefficients of many MVOCs are currently lacking. Equilibrium partition coefficients, such as Henry's law constant, H, are crucial for understanding the environmental behavior of chemicals. This study aims to experimentally determine the H values and their temperature dependence for key MVOCs under temperature relevant to the indoor environment. The H values were determined with the inert gas-stripping (IGS) method and variable phase ratio headspace (VPR-HS) technique. A two-dimensional partitioning model was applied to predict the indoor phase distribution of MVOCs and potential exposure pathways to the residences. The findings show that the MVOCs are likely distributed between the gas and weakly polar (e.g., organic-rich) reservoirs indoors. Temperature and the volume of reservoirs can sensitively affect indoor partitioning. Our results give a more comprehensive view of indoor chemical partitioning and exposure.

In Vitro Systems for Toxicity Evaluation of Microbial Volatile Organic Compounds on Humans: Current Status and Trends

Microbial volatile organic compounds (mVOC) are metabolic products and by-products of bacteria and fungi. They play an important role in the biosphere: They are responsible for inter- and intra-species communication and can positively or negatively affect growth in plants. But they can also cause discomfort and disease symptoms in humans. Although a link between mVOCs and respiratory health symptoms in humans has been demonstrated by numerous studies, standardized test systems for evaluating the toxicity of mVOCs are currently not available. Also, mVOCs are not considered systematically at regulatory level. We therefore performed a literature survey of existing in vitro exposure systems and lung models in order to summarize the state-of-the-art and discuss their suitability for understanding the potential toxic effects of mVOCs on human health. We present a review of submerged cultivation, air-liquid-interface (ALI), spheroids and organoids as well as multi-organ approaches and compare their advantages and disadvantages. Furthermore, we discuss the limitations of mVOC fingerprinting. However, given the most recent developments in the field, we expect that there will soon be adequate models of the human respiratory tract and its response to mVOCs.

Microbial Volatile Organic Compound (VOC)-Driven Dissolution and Surface Modification of Phosphorus-Containing Soil Minerals for Plant Nutrition: An Indirect Route for VOC-Based Plant-Microbe Communications

We investigated the ability of microbial volatile organic compounds (MVOCs) emitted by Bacillus megaterium (a well-known MVOC producer) to modify the dissolution kinetics and surface of hydroxyapatite, a natural soil mineral. Facilitated phosphate release was induced by the airborne MVOCs in a time-dependent manner. Use of each standard chemical of the MVOCs then revealed that acetic and oxalic acids are crucial for the phenomenon. In addition, the ability of such MVOCs to engineer the apatite surfaces was evidenced by FT-IR spectra showing the COO^- band variation with incubation time and the prolonged acceleration of phosphate release during the negligible acidification of the hydroxyapatite-containing solutions. The formation of calcium oxalate was revealed through SEM-EDS and XRD analyses, suggesting that MVOC oxalic acid interacts with calcium ions, leading to the precipitation of calcium oxalate, thus preventing the recrystallization of calcium phosphates. Gel- and soil-based plant cultivation tests employing Arabidopsis thaliana and solid calcium phosphates (i.e., nano- and microsized hydroxyapatites and calcium phosphate dibasic) demonstrated that these MVOC mechanisms facilitate plant growth by ensuring the prolonged supply of plant-available phosphate. The relationship between the growth enhancement and the particle size of the calcium phosphates also substantiated the MVOC sorption onto soil minerals related to plant growth. Given that most previous studies have assumed that MVOCs are a molecular lexicon directly detected by the dedicated sensing machinery of plants, our approach provides a new mechanistic view of the presence of abiotic mediators in the interaction between plants and microbes via MVOCs.

Volatile Organic Compound Profiles Associated with Microbial Development in Feedlot Pellets Inoculated with Bacillus amyloliquefaciens H57 Probiotic

Simple Summary

Our study aimed to confirm that the probiotic, Bacillus amyloliquefaciens strain H57 (H57), manufactured into grain-rich stockfeed pellets, would help maintain the various types of odours of the pellets during an extended storage. Pellets treated with (H57) or without (control, C) were stored either at room temperature or at 5 °C over 3 months. The odours were identified in the pellets, stored at 0, 1, 2 and 3 months, by a gas analysis technique. The change of odour types was greatest in the C pellets stored for 3 months at room temperature (CA3) than all other pellet treatments. The odour types of the H57 pellets aged 2 or 3 months at room temperature were similar to that of C pellets aged 1 or 2 months. Nine odour types of microbial origin were related to the change observed in CA3. These odour types have been previously identified in grains spoiled by mould and thus deserve further evaluation as indicators of the types of mould against which H57 protects as a feed inoculum. These results suggest that H57 can help to maintain the odour of stockfeed pellets, by reducing the rate of microbial spoilage during storage.

Abstract

Mould and bacterial contamination releases microbial volatile organic compounds (mVOCs), causing changes in the odour profile of a feed. Bacillus amyloliquefaciens strain H57 (H57) has the potential ability to inhibit microbial growth in animal feeds. This study tested the hypothesis that H57 influences the odour profile of stored feedlot pellets by impeding the production of mVOCs. The emission of volatile organic compounds (VOCs) of un-inoculated pellets and those inoculated with H57, stored either at ambient temperature (mean 22 °C) or at 5 °C, was monitored at 0, 1, 2, and 3 months by gas chromatography–mass spectrometry. Forty VOCs were identified in all the pellet samples analysed, 24 of which were potentially of microbial and 16 of non-microbial origin. A score plot of the principal component analysis (PCA) showed that the VOC profiles of the pellets stored at ambient temperature changed more rapidly over the 3 months than those stored at 5 °C, and that change was greater in the un-inoculated pellets when compared to the inoculated ones. The bi-plot and correlation loading plots of the PCA indicated that the separation of the un-inoculated pellets from the other treatments over the 3 months was primarily due to nine mVOCs. These mVOCs have been previously identified in grains spoiled by fungi, and could be considered potential markers of the types of fungi that H57 can protect pellets against. These data indicate the ability of H57 to maintain the odour profile and freshness of concentrated feed pellets. This protective influence can be detected as early as 3 months into ambient temperature storage.

Identification of Volatile Sulfur Compounds Produced by Schizophyllum commune

Schizophyllum commune is a causative agent of allergic bronchopulmonary mycosis, allergic fungal rhinosinusitis, and basidiomycosis. Diagnosis of these diseases remains difficult because no commercially available tool exists to identify the pathogen. Unique volatile organic compounds produced by a pathogen might be useful for non-invasive diagnosis. Here, we explored microbial volatile organic compounds produced by S. commune. Volatile sulfur compounds, dimethyl disulfide (48 of 49 strains) and methyl ethyl disulfide (49 of 49 strains), diethyl disulfide (34 of 49 strains), dimethyl trisulfide (40 of 49 strains), and dimethyl tetrasulfide (32 of 49 strains) were detected from headspace air in S. commune cultured vials. Every S. commune strain produced at least one volatile sulfur compound analyzed in this study. Those volatile sulfur compounds were not detected from the cultures of Aspergillus spp. (A. fumigatus, A. flavus, A. niger, and A. terreus), which are other major causative agents of allergic bronchopulmonary mycosis. The last, we examined H₂S detection using lead acetate paper. Headspace air from S. commune rapidly turned the lead acetate paper black. These results suggest that those volatile sulfur compounds are potent targets for the diagnosis of S. commune and infectious diseases.

Effects of Microbes from Coal-Related Commercial Humic Substances on Hydroponic Crop Cultivation: A Microbiological View for Agronomical Use of Humic Substances

Here, coal-related humic substances (HSs) were examined to confirm whether sterilization treatments induce their inferior ability to stimulate lettuce in hydroponic cultivations. Interestingly, a drastic reduction in both lettuce biomass and microbial colony-forming units of the crop culture solutions was observed when the autoclaved HSs were treated. Some microbial genera (i.e., Bacillus and Aspergillus) identifiable in the bare HS-treated hydroponic systems were able to be isolated by direct inoculation of bare HS powders on conventional microbial nutrients, supporting that flourishing microbes in the hydroponic cultivations derive from bare HSs-treated. Moreover, coincubation of some isolated bacterial and fungal strains (i.e., Bacillus and Aspergillus genera) from HSs with lettuce resulted in a significant increase in plant biomass and enhanced resistance to NaCl-related abiotic stresses. Microbial volatile organic compounds renowned for plant stimulation were detected by using solid-phase microextraction coupled with gas chromatography-mass spectrometry. It was finally confirmed that the isolates are capable of utilizing carbon substrates such as pectin and tween 20 or 40, which are relevant to those of microbes isolated from peat and leonardite (i.e., HS extraction sources). Overall, our results suggest that microbiological factors could be considered when commercial coal-related HSs are applied in hydroponic crop cultivations.

Feed Preference Response of Weaner Bull Calves to Bacillus amyloliquefaciens H57 Probiotic and Associated Volatile Organic Compounds in High Concentrate Feed Pellets

Simple Summary

The aim of this work was to confirm that a new probiotic (Bacillus amyloliquefaciens, H57) in stock-feed pellets make cattle want to eat them faster and that H57 increased preference by reducing the rate of microbial spoilage in stored pellets thereby changing the odour of the pellets. Odour was manipulated by manufacturing standard pellets with or without added H57 and then storing half of each for 4 months either in a chiller or at room temperature to make 4 different batches. These were offered, per day for 4 weeks, across 8 automated feed bunks, 1 pellet batch per 2 bunks, in amounts enough to satisfy the daily needs of a single group of 16 young bulls. A given bull could have chosen any of 4 feed batches to eat. The feed batches in the bunks that were emptied the fastest were considered to contain the most preferred batch. The H57 was found to improve preference for pellets but only when they were stored at room temperature and not if they were stored in a chiller. The most preferred pellets had the least concentration of microbial volatile organic compounds. This was consistent with our expectation that H57 inhibits microbial spoilage in feed pellets to improve shelf life.

Abstract

This study tested the hypothesis that Bacillus amyloliquefaciens strain H57 (H57) improves preference by reducing the development of microbial volatile organic compounds (mVOCs) in feed pellets. Sixteen bull calves were, for 4 weeks, provided equal access to a panel of 8 automated feed bunks in a single paddock with some hay. Each bunk contained pellets with (H57) or without (Control) the H57, each aged for 4 months at either ambient or chiller temperature. Each treatment was changed to a new bunk pair position weekly. Relative preference was determined according to weight of pellets remaining per hour per treatment bunk pair per 24 h. Pellets were analysed for volatile organic compounds (VOCs) and the concentrations tested for correlation with relative preference. Calves showed the lowest preference (p < 0.0001) for the Control/Ambient treatment whereas preference for all other treatments (H57/Ambient; H57/Chiller; Control/Chiller) was similar. The Control/Ambient treatment odour profile grouped differently to the other 3 treatments which grouped similarly to each other. Up to 16 mVOCs were determined to have potential as pre-ingestive signals for the extent of microbial spoilage. Further studies are required to find which combination of these mVOCs, when added to pellets, results in feed aversion.

Sixty-One Volatiles Have Phylogenetic Signals Across Bacterial Domain and Fungal Kingdom

Microorganisms are diverse in their genome sequences and subsequently in their encoded metabolic pathways, which enabled them to adapt to numerous environmental conditions. They produce thousands of small molecules, many of which are volatiles in nature and play important roles in signaling in intra- and inter-species to kingdom and domain interactions, survival, or virulence. Many of these compounds have been studied, characterized, and organized in the mVOC 2.0 database. However, such dataset has not been investigated comprehensively in terms of its phylogeny to determine key volatile markers for certain taxa. It was hypothesized that some of the volatiles described in the mVOC 2.0 database could function as a phylogenetic signal since their production is conserved among certain taxa within the microbial evolutionary tree. Our meta-analysis revealed that some volatiles were produced by a large number of bacteria but not in fungal genera such as dimethyl disulfide, acetic acid, 2-nonanone, dimethyl trisulfide, 2-undecanone, isovaleric acid, 2-tridecanone, propanoic acid, and indole (common bacterial compounds). In contrast, 1-octen-3-ol, 3-octanone, and 2-pentylfuran (common fungal compounds) were produced primarily by fungal genera. Such chemical information was further confirmed by investigating genomic data of publicly available databases revealing that bacteria or fungi harbor gene families involved in these volatiles’ biosynthesis. Our phylogenetic signal testing identified 61 volatiles with a significant phylogenetic signal as demonstrated by phylogenetic D statistic P-value < 0.05. Thirty-three volatiles were phylogenetically conserved in the bacterial domain (e.g., cyclocitral) compared to 17 volatiles phylogenetically conserved in the fungal kingdom (e.g., aristolochene), whereas 11 volatiles were phylogenetically conserved in genera from both bacteria and fungi (e.g., geosmin). These volatiles belong to different chemical classes such as heterocyclic compounds, long-chain fatty acids, sesquiterpenoids, and aromatics. The performed approaches serve as a starting point to investigate less explored volatiles with potential roles in signaling, antimicrobial therapy, or diagnostics.

Microbial metabolites elicit distinct olfactory and gustatory preferences in bumblebees

Animals such as bumblebees use chemosensory cues to both locate and evaluate essential resources. Increasingly, it is recognized that microbes can alter the quality of foraged resources and produce metabolites that may act as foraging cues. The distinct nature of these chemosensory cues however and their use in animal foraging remain poorly understood. Here, we test the hypothesis that species of nectar-inhabiting microbes differentially influence pollinator attraction and feeding via microbial metabolites produced in nectar. We first examined the electrophysiological potential for bumblebee (Bombus impatiens) antennal olfactory neurons to respond to microbial volatile organic compounds (mVOCs), followed by an olfactory preference test. We also assessed gustatory preferences for microbial-altered nectar through both no-choice and choice feeding assays. Antennal olfactory neurons responded to some mVOCs, and bees preferred nectar solutions inoculated with the bacterium Asaia astilbes over the yeast Metschnikowia reukaufii based on volatiles alone. However, B. impatiens foragers consumed significantly more Metschnikowia-inoculated nectar, suggesting distinct roles for mVOCs and non-volatile metabolites in mediating both attraction and feeding decisions. Collectively, our results suggest that microbial metabolites have significant potential to shape interspecific, plant-pollinator signalling, with consequences for forager learning, economics and floral host reproduction.

Exposure in vitro to an Environmentally Isolated Strain TC09 of Cladosporium sphaerospermum Triggers Plant Growth Promotion, Early Flowering, and Fruit Yield Increase

A growing number of bacteria and fungi have been found to promote plant growth through mutualistic interactions involving elements such as volatile organic compounds (VOCs). Here, we report the identification of an environmentally isolated strain of Cladosporium sphaerospermum (herein named TC09), that substantially enhances plant growth after exposure in vitro beyond what has previously been reported. When cultured on Murashige and Skoog (MS) medium under in vitro conditions, tobacco seedlings (Nicotiana tabacum) exposed to TC09 cultures for 20 days increased stem height and whole plant biomass up to 25- and 15-fold, respectively, over controls without exposure. TC09-mediated growth promotion required >5 g/L sucrose in the plant culture medium and was influenced by the duration of exposure ranging from one to 10 days, beyond which no differences were detected. When transplanted to soil under greenhouse conditions, TC09-exposed tobacco plants retained higher rates of growth. Comparative transcriptome analyses using tobacco seedlings exposed to TC09 for 10 days uncovered differentially expressed genes (DEGs) associated with diverse biological processes including cell expansion and cell cycle, photosynthesis, phytohormone homeostasis and defense responses. To test the potential efficacy of TC09-mediated growth promotion on agricultural productivity, pepper plants (Capsicum annuum L.) of two different varieties, Cayenne and Minisweet, were pre-exposed to TC09 and planted in the greenhouse to monitor growth, flowering, and fruit production. Results showed that treated pepper plants flowered 20 days earlier and yielded up to 213% more fruit than untreated controls. Altogether the data suggest that exposure of young plants to C. sphaerospermum produced VOCs may provide a useful tool to improve crop productivity.

Application of solid-phase microextraction with gas chromatography and mass spectrometry for the early detection of active moulds on historical woollen objects

The goal of this work was to determine the microbial volatile organic compounds emitted by moulds growing on wool in search of particular volatiles mentioned in the literature as indicators of active mould growth. The keratinolytically active fungi were inoculated on two types of media: (1) samples of wool placed on broths, and (2) on broths containing amino acids that are elements of the structure of keratin. All samples were prepared inside 20 mL vials (closed system). In the first case (1) the broths did not contain any sources of organic carbon, nitrogen, or sulfur, i.e. wool was the only nutrient for the moulds. A third type of sample was historical wool prepared in a Petri dish without a broth and inoculated with a keratinolytically active mould (open system). The microbial volatiles emitted by moulds were sampled with the headspace solid-phase microextraction method. Volatiles extracted on solid-phase microextraction fibers were analyzed in a gas chromatography with mass spectrometry system. Qualitative and quantitative analyses of chromatograms were carried out in search of indicators of metabolic activity. The results showed that there are three groups of volatiles that can be used for the detection of active forms of moulds on woollen objects.

Analysis of Plant Growth-Promoting Effects of Fluorescent Pseudomonas Strains Isolated from Mentha piperita Rhizosphere and Effects of Their Volatile Organic Compounds on Essential Oil Composition

Many species or strains of the genus Pseudomonas have been characterized as plant growth promoting rhizobacteria (PGPR). We used a combination of phenotypic and genotypic techniques to analyze the community of fluorescent Pseudomonas strains in the rhizosphere of commercially grown Mentha piperita (peppermint). Biochemical techniques, Amplified rDNA Restriction Analysis (ARDRA), and 16S rRNA gene sequence analysis revealed that the majority of the isolated native fluorescent strains were P. putida. Use of two Repetitive Sequence-based PCR (rep-PCR) techniques, BOX-PCR and ERIC-PCR, allowed us to evaluate diversity among the native strains and to more effectively distinguish among them. PGPR activity was tested for the native strains and reference strain P. fluorescens WCS417r. Micropropagated M. piperita plantlets were exposed to microbial volatile organic compounds (mVOCs) emitted by the bacterial strains, and plant biomass parameters and production of essential oils (EOs) were measured. mVOCs from 11 of the native strains caused an increase in shoot fresh weight. mVOCs from three native strains (SJ04, SJ25, SJ48) induced changes in M. pierita EO composition. The mVOCs caused a reduction of metabolites in the monoterpene pathway, for example menthofuran, and an increase in menthol production. Menthol production is the primary indicator of EO quality. The mVOCs produced by native strains SJ04, SJ25, SJ48, and strain WCS417r were analyzed. The obtained mVOC chromatographic profiles were unique for each of the three native strains analyzed, containing varying hydrocarbon, aromatic, and alogenic compounds. The differential effects of the strains were most likely due to the specific mixtures of mVOCs emitted by each strain, suggesting a synergistic effect occurs among the compounds present.

Bioprospecting bacterial and fungal volatiles for sustainable agriculture

Current agricultural practice depends on a wide use of pesticides, bactericides, and fungicides. Increased demand for organic products indicates consumer preference for reduced chemical use. Therefore, there is a need to develop novel sustainable strategies for crop protection and enhancement that do not rely on genetic modification and/or harmful chemicals. An increasing body of evidence indicates that bacterial and fungal microbial volatile organic compounds (MVOCs) might provide an alternative to the use of chemicals to protect plants from pathogens and provide a setting for better crop welfare. It is well known that MVOCs can modulate the physiology of plants and microorganisms and in this Opinion we propose that MVOCs can be exploited as an ecofriendly, cost-effective, and sustainable strategy for agricultural practices.