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Measurements of Physiological Stress Responses in C. Elegans
Published on: May 21, 2020
Responsiveness of entomopathogenic fungi to menadione-induced oxidative stress
Rosana F F Azevedo1, Roberta K F Souza1, Gilberto U L Braga2
1Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraíba, São José dos Campos, SP 12244-000, Brazil.
Abstract:
Entomopathogenic fungi are predisposed to ROS induced by heat and UV-A radiation when outside the insect host. When inside the host, they are subject to phagocytic cells that generate ROS to eliminate invading pathogens. The oxidative stress tolerance of the entomopathogenic fungi Aschersonia aleyrodis (ARSEF 430 and 10276), Aschersonia placenta (ARSEF 7637), Beauveria bassiana (ARSEF 252), Isaria fumosorosea (ARSEF 3889), Lecanicillium aphanocladii (ARSEF 6433), Metarhizium acridum (ARSEF 324), Metarhizium anisopliae (ARSEF 5749), Metarhizium brunneum (ARSEF 1187 and ARSEF 5626), Metarhizium robertsii (ARSEF 2575), Tolypocladium cylindrosporum (ARSEF 3392), Tolypocladium inflatum (ARSEF 4877), and Simplicillium lanosoniveum (ARSEF 6430 and ARSEF 6651) was studied based on conidial germination on a medium supplemented with menadione. Conidial germination was evaluated 24 h after inoculation on potato dextrose agar (PDA) (control) or PDA supplemented with menadione. The two Aschersonia species (ARSEF 430, 7637, and 10276) were the most susceptible fungi, followed by the two Tolypocladium species (ARSEF 3392 and 4877) and the M. acridum (ARSEF 324). Metarhizium brunneum (ARSEF 5626) and M. anisopliae (ARSEF 5749) were the most tolerant isolates with MIC 0.28 mM. All fungal isolates, except ARSEF 5626 and ARSEF 5749, were not able to germinate at 0.20 mM.
Insights
Entomopathogenic fungi face oxidative stress from their environment and host defenses. This study assessed the oxidative stress tolerance of various fungal species, identifying Metarhizium anisopliae and Metarhizium brunneum as the most resilient.
Area of Science:
- Mycology
- Insect Pathology
- Biochemistry
Background:
- Entomopathogenic fungi encounter reactive oxygen species (ROS) from environmental factors (heat, UV-A) and host immune responses.
- Understanding oxidative stress tolerance is crucial for effective biological control agent development.
Purpose of the Study:
- To evaluate the oxidative stress tolerance of multiple entomopathogenic fungal species and isolates.
- To identify fungal strains with superior resilience to oxidative stress for potential biocontrol applications.
Main Methods:
- Conidial germination assays were performed on potato dextrose agar (PDA) supplemented with varying concentrations of menadione.
- Menadione was used as a proxy to induce oxidative stress, simulating ROS exposure.
- Germination rates were assessed after 24 hours of incubation.
Main Results:
- Significant variation in oxidative stress tolerance was observed among the tested entomopathogenic fungi.
- Aschersonia aleyrodis, Aschersonia placenta, and Tolypocladium species exhibited high susceptibility to menadione.
- Metarhizium brunneum (ARSEF 5626) and Metarhizium anisopliae (ARSEF 5749) demonstrated the highest tolerance, with a minimum inhibitory concentration (MIC) of 0.28 mM.
- Most isolates failed to germinate at 0.20 mM menadione, except for the two most tolerant Metarhizium isolates.
Conclusions:
- Oxidative stress tolerance varies considerably among entomopathogenic fungal species and isolates.
- Metarhizium brunneum and Metarhizium anisopliae possess robust mechanisms to withstand oxidative stress, making them promising candidates for biocontrol.
- Further research into the specific mechanisms conferring tolerance in these Metarhizium species is warranted.
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