Activity Of Volatile Organic Compounds Research Articles

The effect of β-ionone on bacterial cells: the use of specific lux-biosensors

The diversity of the biological activity of volatile organic compounds (VOCs), including unsaturated ketone β-ionone, promising pharmacological, biotechnological, and agricultural agent, has aroused considerable interest. However, the functional role and mechanisms of action of VOCs remain insufficiently studied. In this work, the response of bacterial cells to the action of β-ionone was studied using specific bioluminescent lux-biosensors containing stress-sensitive promoters. We determined that in Escherichia coli cells, β-ionone induces oxidative stress (PkatG and Pdps promoters) through a specific response mediated by the OxyR/OxyS regulon, but not SoxR/SoxS (PsoxS promoter). It has been shown that β-ionone at high concentrations (50 μM and above) causes a weak induction of the expression from the PibpA promoter and slightly induces the PcolD promoter in the E. coli biosensors; the observed effect is enhanced in the ΔoxyR mutants. This indicates the presence of some damage to proteins and DNA. β-Ionone was found to inhibit the bichaperone-dependent DnaKJE-ClpB refolding of heat-inactivated bacterial luciferase in E. coli wild-type and ΔibpB mutant strains. In the cells of the Gram-positive bacterium Bacillus subtilis 168 pNK-MrgA β-ionone does not cause oxidative stress. Thus, in this work, the specificity of bacterial cell stress responses to the action of β-ionone was shown.

Antifungal activity of volatile organic compounds from essential oils against the postharvest pathogens Botrytis cinerea, Monilinia fructicola, Monilinia fructigena, and Monilinia laxa.

Gray mold and brown rot, caused respectively by Botrytis cinerea and Monilinia spp., are fungal diseases responsible for significant losses during the storage of fruit and vegetables. Nowadays, the control of postharvest diseases is shifting towards more sustainable strategies, including the use of plant secondary metabolites. In this study, the antifungal activity of Origanum vulgare, Thymus vulgaris, Thymus serpyllum, Melaleuca alternifolia, Lavandula officinalis, Lavandula hybrida, Citrus bergamia, Rosmarinus officinalis, Cinnamomum zeylanicum essential oils (EOs) in vapor phase was tested in vitro against B. cinerea, Monilinia fructicola, Monilinia fructigena, and Monilinia laxa. For the experiments, a protocol using a volatile organic compounds (VOC) chamber was designed. Results indicate a dose-dependent inhibitory activity of all the tested EOs, with O. vulgare, T. vulgaris, and T. serpyllum being the most active ones, with minimum inhibitory concentrations (MIC) of 22.73, 45.45, and 22.73 µl/L, respectively, against B. cinerea and a range between 5.64 and 22.73 µl/L against the three Monilinia spp. Overall, B. cinerea presented lower sensitivity to vapor-phase EOs than any of the Monilinia strains, except for the C. zeylanicum EO, which consistently showed higher inhibition against B. cinerea. Among the three Monilinia spp., M. fructicola was the least sensitive, while M. fructigena was the most sensitive. The use of VOC chambers proved to be a reliable protocol for the assessment of antimicrobial activities of EOs. These results suggest that the VOC emitted by the tested EOs are effective towards important decay-causing fungi, and that they could be used for the control of gray mold and brown rot in in vivo trials.

Trichoderma species from rhizosphere of Oxalis corymbosa release volatile organic compounds inhibiting the seed germination and growth of Echinochloa colona

Trichoderma spp. have the potential to act as biocontrol agents for regulating plant growth. In this study, Trichoderma spp. were isolated from the rhizosphere soil of Oxalis corymbosa in sugarcane fields, and six strains were identified as T. koningiopsis, T. afroharzianum, T. atroviride, T. virens and T. asperelloides through morphology and phylogenetic analysis of ITS and tef 1 gene sequences. The activity of volatile organic compounds (VOCs) emitted by Trichoderma spp. was determined using the double-plate chamber method, revealing that five strains significantly inhibited the seed germination and growth of Echinochloa colona. Subsequently, SMPE-GC–MS and Venn analyses unveiled the presence of five common VOCs, namely phenylethyl alcohol, 2,4,6-trichloroanisole, hexadecanoic acid ethyl ester, 10(E),12(Z)-conjugated linoleic acid, and linoleic acid ethyl ester, within Trichoderma spp.. Independently, five compounds were evaluated for their inhibitory effect on the shoot growth of E. colona. Additionally, the results demonstrated that linoleic acid ethyl ester exhibited the highest inhibitory activity, while hexadecanoic acid ethyl ester was the least effective. The inhibitory effect of 2,4,6-trichloroanisole increased with concentration. Hormone analysis results indicated that VOCs influenced the concentration of abscisic acid, resulting in the maintenance of dormancy in E. colona. This study provides compelling evidence for the potential use of Trichoderma as bioherbicides.

Effect of 4-Ethylbenzaldehyde from the Volatilome of Annona muricata on Meloidogyne incognita.

The demand for new soil fumigants has increased as a result of more restrictive legislation regarding the use of pesticides. In the present study, the potent nematicidal activity of volatile organic compounds released by the Annona muricata leaf macerate was demonstrated. In addition, we searched in the A. muricata volatilome for a molecule with potential to be developed as a new fumigant nematicide. In the greenhouse, even the lowest concentration of soursop leaf macerate tested (1.0%) as a biofumigant caused a significant (P < 0.05) reduction in Meloidogyne incognita infectivity and reproduction when compared with the nontreated control (0%). Forty-one compounds were identified through gas chromatography-mass spectrometry analysis, of which three (sabinene, caryophyllene oxide, and 4-ethylbenzaldehyde) were selected for studies against the nematode. Among these compounds, in in vitro trails, only 4-ethylbenzaldehyde showed nematicidal activity at 250 µg ml-1. The effective doses of 4-ethylbenzaldehyde predicted to kill 50 and 95% of the M. incognita second-stage juvenile population after 48 h of exposure were 35 and 88 µg ml-1, respectively. In in vitro tests, 4-ethylbenzaldehyde at 150 µg ml-1 reduced M. incognita egg hatching to values similar (P > 0.05) to those of the commercial nematicide fluensulfone at a concentration of 200 µg ml-1. In plant experiments, as a soil fumigant, 4-ethylbenzaldehyde at a dose of 1 ml/liter of substrate had an effect similar (P > 0.05) to that of the commercial fumigant Dazomet (250 µg ml-1). Therefore, 4-ethylbenzaldehyde shows potential for development as a new nematicide.

Erratum for Zhao et al., "Antagonistic Activity of Volatile Organic Compounds Produced by Acid-Tolerant Pseudomonas protegens CLP-6 as Biological Fumigants To Control Tobacco Bacterial Wilt Caused by Ralstonia solanacearum".

Erratum for Zhao et al., "Antagonistic Activity of Volatile Organic Compounds Produced by Acid-Tolerant Pseudomonas protegens CLP-6 as Biological Fumigants To Control Tobacco Bacterial Wilt Caused by Ralstonia solanacearum".

Study on the Fingerprint and Atmospheric Activity of Volatile Organic Compounds from Typical Industrial Emissions

China is prone to severe surface ozone pollution in summer, so it is very important to understand the source of volatile organic compounds (VOCs) to control ozone formation. In this work, the emission characteristics of 91 VOC components from the plastic products industry, packaging and printing industries, printing ink industry, furniture manufacturing and vehicle manufacturing industries were studied. The results show that there are significant differences between these sources, and for the plastic products industry, alkanes (48%) are the most abundant VOCs. The main emission species in the packaging and printing industry are OVOCs (36%) and alkanes (34%). The proportion of OVOCs in the printing ink (73%) and furniture manufacturing industries (49%) is dominated by VOC emissions; aromatic hydrocarbons (33%), alkanes (33%), and OVOCs (17%) are the main emission species in the vehicle manufacturing industry. At the same time, the ozone generation potential (OFP) and secondary organic aerosol formation potential (SOA) of anthropogenic VOC emissions were evaluated, and the top 10 contributors to OFP and SOA were identified. Toluene, o-xylene, and m-xylene had a significant tendency to form OFP or SOA. Then, a health risk assessment of VOC components was carried out. These data can supplement the existing VOC emission characteristics of anthropogenic emissions, thus enriching the research progress of VOC emission sources.

Antagonistic Activity of Volatile Organic Compounds Produced by Acid-Tolerant Pseudomonas protegens CLP-6 as Biological Fumigants To Control Tobacco Bacterial Wilt Caused by Ralstonia solanacearum.

Tobacco bacterial wilt, which is caused by Ralstonia solanacearum, is a devastating soilborne disease of tobacco worldwide and is widespread in the continuously acidic fields of southern China. Here, the fumigation activity under different pH conditions, component identification, and bioactivity of the volatile organic compounds (VOCs) produced by an acid-tolerant strain, Pseudomonas protegens CLP-6, were investigated. There was a wide antimicrobial spectrum of the VOCs against phytopathogens, including four bacteria, eight fungi, and two oomycetes. The antagonistic activity of the VOCs against R. solanacearum was proportionally correlated with the concentration of the inoculum, amount, culture time, and culture pH for CLP-6. The number of gene copies of R. solanacearum was significantly inhibited by VOCs produced at pH 5.5 in vivo. The control effect of VOCs emitted at pH 5.5 was 78.91% for tobacco bacterial wilt, which was >3-fold greater than that at pH 7.0. Finally, the main volatile compounds were identified by solid-phase microextraction (SPME)-gas chromatography-mass spectroscopy (GC-MS) as S-methyl thioacetate, methyl thiocyanate, methyl disulfide, 1-decene, 2-ethylhexanol, 1,4-undecadiene, 1-undecene, 1,3-benzothiazole, and 2,5-dimethylpyrazine, and the inhibition rates of 1,3-benzothiazole, 2-ethylhexanolmethyl thiocyanate, dimethyl disulfide, and S-methyl thioacetate were 100%, 100%, 88.91%, 67.64%, and 53.29%, respectively. S-Methyl thioacetate was detected only at pH 5.5. In summary, VOCs produced by P. protegens CLP-6 had strong antagonistic activities against phytopathogens, especially R. solanacearum, under acidic conditions and could be used to develop a safe and additive fumigant against R. solanacearum on tobacco and even other Solanaceae crop bacterial wilt diseases in acidic fields. IMPORTANCE VOCs produced by beneficial bacteria penetrate the rhizosphere to inhibit the growth of plant-pathogenic microorganisms; thus, they have the potential to be used as biological agents in controlling plant diseases. Tobacco bacterial wilt, which is caused by the acidophilic pathogen R. solanacearum, is a major bacterial disease in southern China and is prevalent in acidic soil. In this study, we discovered that the VOCs produced by P. protegens CLP-6 had excellent inhibitory effects on important plant pathogens. Moreover, two of the VOCs, namely, 1,3-benzothiazole and 2-ethylhexanol, had excellent inhibitory effect on R. solanacearum, and another VOC substance, methyl thiocyanate, was produced only at pH 5.5. The VOCs produced by the acid-tolerant strain P. protegens CLP-6 may have potential as environment-friendly microbial fumigant agents for bacterial wilt of tobacco or even other Solanaceae crops in acidic soils in China.

Water Enables Lattice Oxygen Activation of Transition Metal Oxides for Volatile Organic Compound Oxidation

A small amount of water can enhance the catalytic combustion activity of volatile organic compounds (VOCs) on transition metal oxides (TMOs), but its intrinsic mechanism is still controversial. Herein, we systematically demonstrate that water molecules can constantly activate lattice oxygen of transition metal oxides to form hydroxyl species theoretically and experimentally. The oxygen atoms of the generated hydroxyl species possess a weak bonding strength with circumjacent metal atoms to easily escape from the surface and attack electron-deficient carbon atoms of VOCs due to their comparatively stronger nucleophilicity, leaving abundant oxygen vacancies as the active sites for subsequent molecular oxygen activation. This work helps us deeply understand the role of water in lattice oxygen activation of transition metal oxides and provides direction for water-related catalysis, such as catalytic VOC combustion, water splitting, water–gas shift reactions, and corrosion.

Nematicidal activity of volatile organic compounds produced by Bacillus altitudinis AMCC 1040 against Meloidogyne incognita

The application of nematicidal microorganisms and their virulence factors provides more opportunities to control root-knot nematodes. Bacillus altitudinis AMCC 1040, previously isolated from suppressive soils, showed significant nematicidal activity, and in this study, nematicidal substances produced by Bacillus altitudinis AMCC 1040 were investigated. The results of the basic properties of active substances showed that these compounds have good thermal stability and passage, are resistant to acidic environment and sensitive to alkaline conditions. Further analysis showed that it is a volatile component. Using HS-SPME-GC/MS, the volatile compounds produced by Bacillus altitudinis AMCC 1040 were identified and grouped into four major categories: ethers, alcohols, ketone, and organic acids, comprising a total of eight molecules. Six of them possess nematicidal activities, including 2,3-butanedione, acetic acid, 2-isopropoxy ethylamine, 3-methylbutyric acid, 2-methylbutyric acid and octanoic acid. Our results further our understanding of the effects of Bacillus altitudinis and its nematicidal metabolites on the management of Meloidogyne incognita and may help in finding less toxic nematicides to control root knot nematodes.

Antifungal Activity of Volatile Organic Compounds from Bacillus velezensis CE 100 against Colletotrichum gloeosporioides

Colletotrichum gloeosporioides is the most prevalent phytopathogen, causing anthracnose disease that severely affects the production of various fruit trees, including walnut and jujube. In this study, the volatile organic compounds (VOCs) from Bacillus velezensis CE 100 disrupted the cell membrane integrity of C. gloeosporioides and reduced the spore germination by 36.4% and mycelial growth by 20.0% at a bacterial broth concentration of 10%, while the control group showed no antifungal effect. Based on the headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) analysis, seven VOCs were identified from the headspace of B. velezensis CE 100. Out of the seven VOCs, 5-nonylamine and 3-methylbutanoic acid were only detected in the headspace of B. velezensis CE 100 but not in the control group. Both 5-nonylamine and 3-methylbutanoic acid showed significant antifungal activity against the spore germination and mycelial growth of C. gloeosporioides. Treatment with 100 µL/mL of 5-nonylamine and 3-methylbutanoic acid suppressed the spore germination of C. gloeosporioides by 10.9% and 30.4% and reduced mycelial growth by 14.0% and 22.6%, respectively. Therefore, 5-nonylamine and 3-methylbutanoic acid are the potential antifungal VOCs emitted by B. velezensis CE 100, and this is the first report about the antifungal activity of 5-nonylamine against C. gloeosporioides.

The interplay between selective etching induced cation defects and active oxygen species for volatile organic compounds degradation

Surface electronic structure of transition metal oxides plays a vital role in determining the catalytic performance. Herein, we present a selective etching strategy to tune the surface cation defect of the CuWO4 (CW) catalyst for improving the catalytic activity of volatile organic compounds (VOCs). HRTEM, SEM-EDS, EPR, and XPS show that the chelation of metal ions in acetic acid and ammonium hydroxide can help to remove a small number of surface cations in CW to form suitable W defects. Cu L-edge and O K-edge XAS, Raman, and O 1s XPS spectrum illustrate that cation defects can improve the hybrid orbits of metal-oxygen bonds, which increases the activity of surface lattice oxygen and metal sites. In-situ DRIFTS spectra reveal that CW with cation defects can easily adsorb toluene, cleave and oxidize benzene ring, and desorb CO2 because of more surface dangling bonds and active oxygen species. Therefore, the toluene conversion rates of CW-Aci and CW-Alk are much higher than CW in VOCs degradation and the catalytic performance improved 33 times and 22 times at 200 °C, respectively. This study offers a new pathway in engineering surface electronic structure and highlights the interplay between cation defects and active oxygen species.

Antifungal activity of volatile organic compounds (VOCs) produced by Streptomyces olivochromogenes S103 against Candida albicans

Antifungal activity of volatile organic compounds (VOCs) produced by Streptomyces olivochromogenes S103 against Candida albicans

Antifungal activity of volatile organic compounds from Streptomyces sp. strain S97 against Botrytis cinerea

ABSTRACT The antifungal activity of volatile organic compounds (VOCs) from 10 Streptomyces isolates was tested using the double-dish chamber method. The VOCs-producing strain S97 exhibited the highest inhibitory effect against Botrytis cinerea mycelium growth. This isolate was identified as Streptomyces sp. with high similarity with Streptomyces lydicus based on morphological and physiological properties, as well as 16S rRNA gene sequence analysis. S97 VOCs analysis was performed by SPME–GC–MS revealing the presence of 14 compounds including three major terpenoids: 3-carene 2,5-dione, geosmin, beta-cubebene and one phenolic compound Phenol, 2-(1,1-dimethylethyl)-6-methyl- representing 43%, 20%, 11% and 9.34% of total produced VOCs, respectively. S97 VOCs inhibited mycelial growth of Rhizoctonia solani and Phoma medicaginis by 95%, Fusarium solani by 69% and Fusarium oxysporum and Sclerotium rolfsii by 20%. The in vivo test carried out on ripe strawberries inoculated by Botrytis cinerea conidia showed that S97 VOCs inhibited the development of grey mould symptoms on fruits by more than 87% compared to untreated control strawberries. Further, light microscope observations revealed 60% swelling and 21% crumbling of B. cinerea conidia when treated with S97 VOCs. Fungal mycelium also showed deep structural alterations with S97 VOCs after 48 h incubation. Strain S97 exhibited strong fumigation potential to control phytopathogenic fungi.

Antagonistic activity of volatile organic compounds of endophytic bacteria from sword brake fern (Pteris ensiformis) against soil-borne fungal pathogens

The use of endophytic bacteria in the control of plant diseases, especially soil pathogenic fungi such as showed good results. Endophytic bacteria have various mechanisms to control plant pathogen, but the mechanism of endophytic bacteria in producing volatile organic compounds (VOCs) has not been widely studied. The objective of this research was to evaluated the antagonistic activity of VOCs produced by endophytic bacteria from the nail sword (Pteris ensiformis) aginst three soil borne pathogen fungus, R. solani, S. rolfsii and Fusarium sp. Endophytic bacterial isolates used were APE15, APE22, APE33, and APE35. The study was conducted by cupping method to determine the inhibition of endophytic bacteria VOCs against three soil borne fungal pathogens. GC-MS analysis was conducted to determine the content of volatile compounds produced by endophytic bacteria. The results showed that four endophytic bacterial isolates can inhibited R. solani growth (92.11%-96.05%), S.rolfsii (87.28%-93.10%), and Fusarium sp. (27.73%-57.55%). The GC-MS analysis showed that there were several antifungal compounds detected i.e. octanal, cytronellyl acetate, silane, 9-octacenamide, n-dimetylpalmitamide, and isobutyryl chloride. Octanal was presumed as the most influential compound that inhibited the three soil borne fungal pathogens because it was a dominant compound was detected.

Antifungal volatiles from medicinal herbs suppress Fusarium oxysporum f. sp. lycopersici

Medicinal herbs are the potential sources for antimicrobial compounds against soil-borne pathogens. The present investigation focuses on assessing the efficacy of antifungal activity of volatile organic compounds (VOCs) produced by seven different medicinal herbs in the suppression of F. oxysporum f.sp. lycopercisi, the causal agent of wilt disease in tomato plants. Among the seven samples tested in-vitro, the blend of VOCs emitted from mint (Mentha spicata) leaves inhibited the mycelial growth of F. o. f.sp. lycopercisi up to 41.88% followed by lemongrass (39.44%) and nochi leaves (34.66%). The important VOCs emitted by mint and lemongrass samples were identified through Headspace – Gas chromatography coupled with Mass Spectrophotometry (HS-GCMS) which revealed the presence of around 25 different compounds with varied functional groups. Among them -(-) carvone obtained from mint leaves had the highest relative abundance (2.08% peak area at 10.25 RT). In addition, geraniol and citronellol were also present with a peak area percentage of 15.85 at 10.37 RT and 5.27 at 9.97 RT, respectively. Pure compounds of carvone, geraniol and citronellol (Sigma Aldrich) along with plant samples were also tested in vitro for comparison on the inhibition of mycelial growth of F. oxysporum f. sp. lycopercisi. Among the samples, citronellol was found to be the most effective and suppressed the wilt pathogen up to 100% at 500 ppm, followed by carvone (up to 90% inhibition) in the partition plate method. The results indicated that VOCs produced from mint and lemongrass could be explored with an additive effect for the management of F. oxysporum f.sp. lycopercisi along with other Integrated Disease Management (IDM) practices.

Fungicidal Activity of Volatile Organic Compounds Emitted by Burkholderia gladioli Strain BBB-01.

A Burkholderia gladioli strain, named BBB-01, was isolated from rice shoots based on the confrontation plate assay activity against several plant pathogenic fungi. The genome of this bacterial strain consists of two circular chromosomes and one plasmid with 8,201,484 base pairs in total. Pangenome analysis of 23 B. gladioli strains suggests that B. gladioli BBB-01 has the closest evolutionary relationship to B. gladioli pv. gladioli and B. gladioli pv. agaricicola. B. gladioli BBB-01 emitted dimethyl disulfide and 2,5-dimethylfuran when it was cultivated in lysogeny broth and potato dextrose broth, respectively. Dimethyl disulfide is a well-known pesticide, while the bioactivity of 2,5-dimethylfuran has not been reported. In this study, the inhibition activity of the vapor of these two compounds was examined against phytopathogenic fungi, including Magnaporthe oryzae, Gibberella fujikuroi, Sarocladium oryzae, Phellinus noxius and Colletotrichum fructicola, and human pathogen Candida albicans. In general, 2,5-dimethylfuran is more potent than dimethyl disulfide in suppressing the growth of the tested fungi, suggesting that 2,5-dimethylfuran is a potential fumigant to control plant fungal disease.

Identification and control of the volatile organic compounds activity in confined environments (Mosques)

Mosques within the professional environments such as universities, banks and shopping malls possess different features that from the public mosques. These mosques are of relatively smaller size, less airy, populated for a shorter duration of the day and the visitors with more formal dressing. All these factors contribute to an increased activity of Volatile Organic Compounds (VOCs) generated by the visitors. Improper drying of the wet feet after ablution and/or prolonged wearing of socks, while being in professional environments, further worsens the situation. A prolonged activity of these VOCs in confined environments is not only unpleasant but also poses certain health issues. This study aims at identification of the need to control this activity within an acceptable limit by deploying a low-cost smart computational configuration of sensor array. The configuration parameters depend on a number of factors such as mosque space, ventilation, air conditioning and the quantity and quality of VOCs generated on average. Pertinent VOC data monitoring, computing and averaging across a network is done in real-time using mobile sensing stations. A proof of concept-based technical feasibility on the adoption of a control strategy is conducted by establishing an acceptable threshold level for the VOCs activity in varying conditions. As the sensitivity of the sensor and the lifespan & proliferation of the VOCs are affected by the humidity, temperature and the air circulation, these factors are closely monitored. Mosque being a sacred place, all these experiments are constrained to be conducted in a controlled manner without any disturbance whatsoever to the environment, visitors and the religious activities being performed.

Antifungal effect of volatile organic compounds produced by Pseudomonas chlororaphis subsp. aureofaciens SPS-41 on oxidative stress and mitochondrial dysfunction of Ceratocystis fimbriata

Ceratocystis fimbriata is the pathogen of black rot disease, which widely exists in sweet potato producing areas all over the world. The antifungal activity of volatile organic compounds (VOCs) released by Pseudomonas chlororaphis subsp. aureofaciens SPS-41 against C. fimbriata was reported in our previous study. In this study, we attempted to reveal the underlying antifungal mechanism of SPS-41 volatiles. Our results showed that the VOCs released by SPS-41 caused the morphological change of hyphae, destroyed the integrity of cell membrane, reduced the content of ergosterol, and induced massive accumulation of reactive oxygen species in C. fimbriata cells. Furthermore, SPS-41 fumigation decreased the mitochondrial membrane potential, acetyl-CoA and pyruvate content of C. fimbriata cells, as well as the mitochondrial dehydrogenases activity. In addition, the VOCs generated by SPS-41 reduced the intracellular ATP content and increased the extracellular ATP content of C. fimbriata. In summary, SPS-41 fumigation exerted its antifungal activity by inducing oxidative stress and mitochondrial dysfunction in C. fimbriata.

Antibacterial Activity of Volatile Organic Compounds Produced by the Octocoral-Associated Bacteria Bacillus sp. BO53 and Pseudoalteromonas sp. GA327.

The present research aimed to evaluate the antibacterial activity of volatile organic compounds (VOCs) produced by octocoral-associated bacteria Bacillus sp. BO53 and Pseudoalteromonas sp. GA327. The volatilome bioactivity of both bacteria species was evaluated against human pathogenic antibiotic-resistant bacteria, methicillin-resistant Staphylococcus aureus, Acinetobacter baumanni, and Pseudomonas aeruginosa. In this regard, the in vitro tests showed that Bacillus sp. BO53 VOCs inhibited the growth of P. aeruginosa and reduced the growth of S. aureus and A. baumanni. Furthermore, Pseudoalteromonas sp. GA327 strongly inhibited the growth of A. baumanni, and P. aeruginosa. VOCs were analyzed by headspace solid-phase microextraction (HS-SPME) joined to gas chromatography-mass spectrometry (GC-MS) methodology. Nineteen VOCs were identified, where 5-acetyl-2-methylpyridine, 2-butanone, and 2-nonanone were the major compounds identified on Bacillus sp. BO53 VOCs; while 1-pentanol, 2-butanone, and butyl formate were the primary volatile compounds detected in Pseudoalteromonas sp. GA327. We proposed that the observed bioactivity is mainly due to the efficient inhibitory biochemical mechanisms of alcohols and ketones upon antibiotic-resistant bacteria. This is the first report which describes the antibacterial activity of VOCs emitted by octocoral-associated bacteria.

Broad-Spectrum Activity of Volatile Organic Compounds from Three Yeast-like Fungi of the Galactomyces Genus Against Diverse Plant Pathogens

The application of antagonistic fungi for plant protection has attracted considerable interest because they may potentially replace the use of chemical pesticides. Antipathogenic activities confirmed in volatile organic compounds (VOCs) from microorganisms have potential to serve as biocontrol agents against pre- and post-harvest diseases. In the present study, we investigated Galactomyces fungi isolated from rotten leaves and the rhizosphere of cherry tomato (Lycopersicon esculentum var. cerasiforme). VOCs produced by Galactomyces fungi negatively affected the growth of phytopathogenic fungi and the survival of nematodes. Mycelial growths of all nine examined phytopathogenic fungi were inhibited on agar plate, although the inhibition was more intense in Athelia rolfsii JYC2163 and Cladosporium cladosporioides JYC2144 and relatively moderate in Fusarium sp. JYC2145. VOCs also efficiently suppressed the spore germination and mycelial growth of A. rolfsii JYC2163 on tomatoes. The soil nematode Caenorhabditis elegans exhibited higher mortality in 24 h in the presence of VOCs. These results suggest the broad-spectrum activity of Galactomyces fungi against various plant pathogens and the potential to use VOCs from Galactomyces as biocontrol agents.