Fungi that digest wood in novel ways could fuel new avenues of research on cellulosic ethanol, and suggest a need to move beyond traditional classification systems. ungi that digest wood are typically categorized as white rots, which degrade both lignin and cellulose, or brown rots, which only have enzymes that act on cellulose. But two newly sequenced species are capable of digesting lignin, even though they lack the enzymes typically found in white rots, according to a study published this week (June 23) in PNAS. The species, Botryobasidium botryosum and Jaapia argillacea, appeared to be white-rot fungi based on the microscopic patterns they created in decomposing wood. “But at the molecular level, we found that the key enzymes considered markers of white-rot fungi were missing,” said Igor Grigoriev of the US Department of Energy (DOE) Joint Genome Institute (JGI) in Walnut Creek, California, who led the work. The results suggest “a continuum rather than a dichotomy between the white-rot and brown-rot modes of wood decay,” and highlight the need for a more nuanced categorization of rot types, according to the authors. Identifying the decay mechanisms in these new species could also have practical applications in the production of cellulosic biofuels, said Grigoriev. “There was a lot of suspicion within the scientific community that the decay mechanisms wouldn’t be as straightforward as they’re currently classified, but the data wasn’t quite there,” said fungal biologist Dan Eastwood of Swansea University in Wales, who was not involved with the work. “This study brings more genomes to the point where we are plugging important gaps to say it’s more complicated than [just two kinds of rot].” Eastwood likened the structure of wood to that of reinforced concrete, where lignin forms the concrete, and cellulose the iron rods that run through and support the structure. Brown-rot fungi digest only the cellulose, leaving behind a dark- colored, brittle mass of lignin. White- rot fungi often digest lignin first, leaving behind long strands of cellulose in a fibrous mass. The two kinds of decay create different porous structures in wood. Source: bit.ly/1ir7ita
Posted on: Tue, 24 Jun 2014 07:56:20 +0000
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