Sally B. Padhi

18 Fungal and Bacterial Volatile Organic Compounds: An Overview and Their Role as Ecological Signaling Agents

Both fungi and bacteria emit many volatile organic compounds (VOCs) as mixtures of low molecular mass alcohols, aldehydes, esters, terpenoids, thiols, and other small molecules that easily volatilize. Most determination (separation and identification) of VOCs now relies on gas chromatography–mass spectrometry (GC-MS) but developments in “electronic nose” technology promise to revolutionize the field. Microbial VOC profiles are both complex and dynamic: the compounds produced and their abundance vary with the producing species, the age of the colony, water availability, the substrate, the temperature, and other environmental parameters. The single most commonly reported volatile from fungi is 1-octen-3-ol which is a breakdown product of linoleic acid. It functions as a hormone within many fungal species, serves as both an attractant and deterrent for certain species of arthropods, and exhibits toxicity at relatively low concentrations in model systems. Bacterial and fungal VOCs have been studied by scientists from a broad range of subdisciplines in both theoretical and applied contexts. VOCs are exploited for their food and flavor properties, their use as indirect indicators of microbial growth, their ability to stimulate plant growth, and their ability to attract insect pests. Because these compounds can diffuse a long way from their point of origin, they are excellent chemical signaling molecules (semiochemicals) in non-aqueous habitats and facilitate the ability of microbes to engage in “chemical conversations.” The physiological effects of bacterial and fungal VOCs in host–pathogen relationships and in mediating interspecific associations in natural ecosystem functioning is an emerging frontier for future research.

Electrophoresis of the Proteins of the Nuclear Polyhedrosis Virus of Porthetria dispar

The nuclear polyhedrosis virus (NPV) of Porthetria dispar (gypsy moth) was isolated and purified in order to examine its protein components, which have been little studied in insect viruses. Virus par

Two volatile-phase alcohols inhibit growth of Pseudogymnoascus destructans, causative agent of white-nose syndrome in bats

ABSTRACT In North America, Pseudogymnoascus destructans infects hibernating bats within caves and other hibernacula causing high mortalities. We have sought a potential fumigation strategy that can be deployed within a contained area, using an agent that already has been determined to be safe for environmental application. We here report the efficacy of 1-octen-3-ol (“mushroom alcohol”) and 1-hexanol against P. destructans. At 50 ppm and 100 ppm, vapours of racemic 1-octen-3-ol are fungicidal to P. destructans at 15ºC after 21 days incubation, while exposure to 5 and 10 ppm is fungistatic. The six-carbon alcohol 1-hexanol is not as effective, although at 50 and 100 ppm, vapours of this compound inhibited growth of the fungus.

Inactivation of nuclear polyhedrosis virus on egg surfaces of the gypsy moth, Lymantria dispar. Hatching efficiency and virus infection of treated eggs and second generation larvae

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Chemical characterization studies of the nuclear polyhedrosis virus of Porthetria dispar

Abstract The nuclear polyhedrosis virus (NPV) of Porthetria dispar was isolated and purified through a two-step zonal centrifugation procedure. The LD50 of the purified NPV was determined by a dose-response assay. Quantitative analyses were made of whole polyhedra and of separated fractions of polyhedral protein, virus rods, and denatured material, i.e., the pellet obtained from low speed centrifugation of dissolved polyhedra, to determine the protein, DNA, and “RNA” (orcinol-positive material) present in this NPV. Approximately one-half the “RNA” was present in the denatured material. Trace elements were also determined, and four, Fe, Mg, Cu, and Zn, of the ten assayed were present in the polyhedral protein fraction, while only Mg and Zn were in the virus rod fraction.

Pseudogymnoascus destructans: Causative Agent of White-Nose Syndrome in Bats Is Inhibited by Safe Volatile Organic Compounds

White-nose syndrome (WNS) is caused by Pseudogymnoascus destructans, a psychrophilic fungus that infects hibernating bats and has caused a serious decline in some species. Natural aroma compounds have been used to control growth of fungal food storage pathogens, so we hypothesized that a similar strategy could work for control of P. destructans. The effectiveness of exposure to low concentrations of the vapor phase of four of these compounds was tested on mycelial plugs and conidiospores at temperatures of 5, 10 and 15 °C. Here we report the efficacy of vapor phase mushroom alcohol (1-octen-3-ol) for inhibiting mycelial and conidiospore growth of P. destructans at 0.4 and 0.8 µmol/mL and demonstrate that the R enantiomer of this compound is more effective than the S enantiomer, supporting the finding that biological systems can be sensitive to stereochemistry. Further, we report that vapor phase leaf aldehyde (trans-2-hexenal), a common aroma compound associated with cut grass odors and also the major volatile compound in extra virgin olive oil, is more effective than mushroom alcohol. At 0.05 µmol/mL, trans-2-hexenal is fungicidal to both conidiospores and mycelia of P. destructans.