Aspergillus flavus is widely studied due to its production of aflatoxin, a naturally occurring toxin that contaminates crops worldwide. Aflatoxin continues to be a great agricultural threat leading to yield losses of millions of dollars in the US. It also causes alfatoxicosis in humans and animals which may develop into liver cancer. While many studies focus on the production of aflatoxin as a mutagenic secondary metabolite, little is known about the extracellular enzymatic activities that may facilitate the germination of A. flavius. In our study we monitor extracellular glucose oxidase activity during different stages of germination by coupling atomic force microscopy (AFM) with scanning electrochemical microscopy. The glucose oxidase activity is monitored through a redox cycling where glucose is oxidized to gluconic acid by the secreted enzyme. Hexaammineruthenium (III) chloride (Ruhex) will be used as a mediator. To achieve high sensitivity for monitoring glucose oxidase activity at single cell levels, we will use insulated Pt probes with a tip radius of about 200 nm. The morphological changes and the physical properties (e.g., fluidity and topography) of the cell walls will be examined with AFM during the spore’s transition from the dormant state to the germination state. We will report on an elevated glucose oxidase activity during germination, which might provide insight on how the fungus develops to its mature form and aid the research in developing control strategies that will reduce the pathogenicity of A. flavus.

Monitoring extracellular glucose oxidase activity of Aspirigillus flavus during germination using scanning probe microscopy

251st National Meeting (2016)

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