Production of hydroxyl radicals by lichens via extracellular hydroquinone-driven redox cycling.
Year: 2016
Type: dissertation
Abstract: Hydroxyl radicals play crucial roles in biology, and these include the breakdown of lignocellulosic residues in the soil, which may allow species to live a partially saprotrophic lifestyle, and the breakdown of potentially toxic soil chemicals.The aim of this study was to conduct a survey to determine if the extracellular hydroxyl radical formation occurs in a range of lichenized ascomycetes.In this study, the production of hydroxyl radicals by lichen via an extracellular redox cycling process was examined.It was also tested whether lichen species could decolorize different synthetic dyes.There is evidence that free-living white and brown rot fungi can generate hydroxyl radicals using extracellular redox cycling.Results showed that given a quinone and chelated ferric ions, many lichens can readily produce hydroxyl radicals, and at the same time reduce ferric ion to ferrous ions.There were no significant differences in the rate of hydroxyl radical formation in non-Peltigeralean and Peltigeralean lichens.While in white rot fungi extracellular redox enzymes have been proposed to be involved in hydroxyl radical generation however, in lichens hydroxyl radical production is not correlated to the activities of laccase and peroxidase.Therefore, it seems likely that the radicals are produced by Fenton chemistry, by a mechanism like that proposed for brown rot fungi.In these fungi, a surface reductase reduces a quinone to a hydroquinone, which reacts directly with ferric ions non-enzymatically generating a quinone radical.This radical spontaneously re-forms a quinone, producing H2O2.The resulting ferrous ion and H2O2 can react together to give theResults indicate that lichens can decolorize a range synthetic dyes on their own, but when given quinones and chelated Fe decolorisation was greatly enhanced as this will facilitate the formation of hydroxyl radicals.RBBR was the best metabolized dye and Usnea undulata was the most effective lichen species from the list of dye and lichen tested.However, adding H2O2 concentration had little effect on dye decolorisation.
Author: Calvin Eddington Moyo
Language: English
Topic: Lichen and fungal ecology
Domain: Life Sciences
Open Access status: green
Award: G1310654914
OpenAlex ID: W2786009580