Estimating CO2 and VOCs production of Colletotrichum fragariae and Rhizopus stolonifer grown in cold stored strawberry fruit.

The aim of this work was to investigate the early detection of anthracnose and soft rot diseases in cold stored strawberry fruit by evaluating the CO2 and volatile organic compounds (VOCs) released by the fungi Colletotrichum fragariae and Rhizopus stolonifer. Strawberries were stored at 5, 10 and 21 °C (control group) and the VOCs and CO2 production of inoculated and non-inoculated strawberries were followed by gas chromatography. To evaluate and estimate the growth of both fungi, the CO2 data were fitted to the Gompertz model. Data of the VOCs released at the end of the fungal growth were analyzed using principal components analysis (PCA) to discriminate between infected and non-infected strawberries. The results showed that fungal growth was affected by temperature and C. fragariae had a maximum growth after 14.6 h at 5 °C and R. stolonifer at 21 °C after 45.2 h. On the other hand, through VOCs released by C. fragariae and R. stolonifer and PCA, four groups were obtained: a) strawberry infected with C. fragariae, stored at 10 °C, b) strawberry infected with R. stolonifer, stored at 21 °C, c) control group kept at 10 °C and, d) strawberry infected with C. fragariae and control group (5 and 21 °C), and strawberry infected with R. stolonifer at 5 and 10 °C. In conclusion, CO2 and VOCs released by C. fragariae and R. stolonifer on strawberries could infer the presence of anthracnose and soft rot during storage of the fruit at low temperature.

Prodigiosin, Violacein, and Volatile Organic Compounds Produced by Widespread Cutaneous Bacteria of Amphibians Can Inhibit Two Batrachochytrium Fungal Pathogens.

Symbiotic bacteria can produce secondary metabolites and volatile compounds that contribute to amphibian skin defense. Some of these symbionts have been used as probiotics to treat or prevent the emerging disease chytridiomycosis. We examined 20 amphibian cutaneous bacteria for the production of prodigiosin or violacein, brightly colored defense compounds that pigment the bacteria and have characteristic spectroscopic properties making them readily detectable, and evaluated the antifungal activity of these compounds. We detected violacein from all six isolates of Janthinobacterium lividum on frogs from the USA, Switzerland, and on captive frogs originally from Panama. We detected prodigiosin from five isolates of Serratia plymuthica or S. marcescens, but not from four isolates of S. fonticola or S. liquefaciens. All J. lividum isolates produced violacein when visibly purple, while prodigiosin was only detected on visibly red Serratia isolates. When applied to cultures of chytrid fungi Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal), prodigiosin caused significant growth inhibition, with minimal inhibitory concentrations (MIC) of 10 and 50 µM, respectively. Violacein showed a MIC of 15 µM against both fungi and was slightly more active against Bsal than Bd at lower concentrations. Although neither violacein nor prodigiosin showed aerosol activity and is not considered a volatile organic compound (VOC), J. lividum and several Serratia isolates did produce antifungal VOCs. White Serratia isolates with undetectable prodigiosin levels could still inhibit Bd growth indicating additional antifungal compounds in their chemical arsenals. Similarly, J. lividum can produce antifungal compounds such as indole-3-carboxaldehyde in addition to violacein, and isolates are not always purple, or turn purple under certain growth conditions. When Serratia isolates were grown in the presence of cell-free supernatant (CFS) from the fungi, CFS from Bd inhibited growth of the prodigiosin-producing isolates, perhaps indicative of an evolutionary arms race; Bsal CFS did not inhibit bacterial growth. In contrast, growth of one J. lividum isolate was facilitated by CFS from both fungi. Isolates that grow and continue to produce antifungal compounds in the presence of pathogens may represent promising probiotics for amphibians infected or at risk of chytridiomycosis. In a global analysis, 89% of tested Serratia isolates and 82% of J. lividum isolates were capable of inhibiting Bd and these have been reported from anurans and caudates from five continents, indicating their widespread distribution and potential for host benefit.

Growth media affect the volatilome and antimicrobial activity against Phytophthora infestans in four Lysobacter type strains.

Bacterial volatile organic compounds (VOCs) play important ecological roles in soil microbial interactions. Lysobacter spp. are key determinants of soil suppressiveness against phytopathogens and the production of non-volatile antimicrobial metabolites has been extensively characterised. However, the chemical composition and antagonistic properties of the Lysobacter volatilome have been poorly investigated. In this work, VOC emission profiles of four Lysobacter type strains grown on a sugar-rich and a protein-rich medium were analysed using solid-phase microextraction gas chromatography-mass spectrometry and proton transfer reaction-time of flight-mass spectrometry. Lysobacter antibioticus, L. capsici, L. enzymogenes and L. gummosus type strains were recognised according to their volatilome assessed using both headspace mass spectrometry methods Moreover, the chemical profiles and functional properties of the Lysobacter volatilome differed according to the growth medium, and a protein-rich substrate maximised the toxic effect of the four Lysobacter type strains against Phytophthora infestans. Antagonistic (pyrazines, pyrrole and decanal) and non-antagonistic (delta-hexalactone and ethanol) VOCs against Ph. infestans or putative plant growth stimulator compounds (acetoin and indole) were mainly emitted by Lysobacter type strains grown on protein- and sugar-rich media respectively. Thus nutrient availability under soil conditions could affect the aggressiveness of Lysobacter spp. and possibly optimise interactions of these bacterial species with the other soil inhabitants.

Short-term effect of strontium- and zinc-containing toothpastes and mouthrinses on volatile sulphur compounds in morning breath: a randomized, double-blind, cross-over clinical study.

Zinc (Zn) reduces the formation of volatile sulphur compounds (VSCs) associated with oral malodour. Although strontium (Sr) is included in some products for reducing dental hypersensitivity, it may also have anti-halitosis properties. This randomized, double-blind, cross-over clinical study compared the anti-VSC effect of brushing with commercial toothpastes and rinses containing Zn and Sr. The volunteers (n = 30) either brushed/rinsed with/without tongue brushing using Zn-containing toothpaste/rinse, Sr-containing toothpaste/rinse, or placebo (control). Volatile sulphur compounds [hydrogen sulphide (H2 S) and methyl mercaptan (CH3 SH)] were measured, in morning breath, using gas chromatography. The anti-VSC effects of the test toothpastes and test rinses were significantly better than the anti-VSC effects of the respective controls. Toothbrushing with test toothpastes gave median reductions, compared with the control, of 70% for H2 S and 55-57% for CH3 SH. Rinsing with the Sr- and Zn-containing solutions had the same anti-VSC effect as toothbrushing and tooth- and tongue brushing with the Sr- and Zn-containing toothpastes. Zinc-containing rinse resulted in a significantly higher median salivary level of Zn compared with brushing with Zn-containing toothpaste, although this effect did not correlate with the anti-VSC effect. It can be concluded that the Sr- and Zn-containing toothpastes and the Zn- and Sr-containing rinses, when used in the evening, are equally effective in reducing morning-breath VSCs the following day.

Characterization of phenolic constituents inhibiting the formation of sulfur-containing volatiles produced during garlic processing.

Garlic (Allium sativum L.), which is a widely distributed plant, is globally used as both spice and food. This study identified five novel phenolic compounds, namely, 8-(3-methyl-(E)-1-butenyl)diosmetin, 8-(3-methyl-(E)-1-butenyl)chrysin, 6-(3-methyl-(E)-1-butenyl)chrysin, and Alliumones A and B, along with nine known compounds 6-14 from the ethanol extract of garlic. The structures of these five novel phenolic compounds were established via extensive 1D- and 2D-nuclear magnetic resonance spectroscopy experiments. The effects of the phenolic compounds isolated from garlic on the enzymatical or nonenzymatical formation of sulfur-containing compounds produced during garlic processing were examined. Compound 12 significantly reduced the thermal decomposition of alliin, whereas compound 4 exhibited the highest percentage of alliinase inhibition activity (36.6%).

Tea catechin EGCg suppresses the mgl gene associated with halitosis.

Epigallocatechin gallate (EGCg), the main antimicrobial tea catechin, has been reported to inhibit growth and virulence factors of oral pathogens in vitro. Although the mechanism is unclear, the potential of EGCg in reducing halitosis caused by volatile sulfur compounds (VSCs) has been suggested. This study tested the hypothesis that EGCg reduces VSCs by suppressing mgl, the gene encoding L-methionine-α-deamino-γ-mercaptomethane-lyase, responsible for methyl mercaptan (CH3SH) production by oral anaerobes. In this study, the effect of EGCg on in vitro growth, CH3SH production, and mgl gene expression in P. gingivalis W83 was investigated. EGCg inhibited growth of P. gingivalis W83 (MIC = 97.5 µg/mL) and was bactericidal (MBC = 187.5 µg/mL). At sub-MIC levels, EGCg inhibited CH3SH production, and mgl mRNA and protein expression (p < 0.05). We conclude that EGCg may represent a natural and alternative agent to the antimicrobial chemicals currently available for halitosis control.