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Speaker Abstract

"Lignocellulose degradation in wood feeding insects"

Scott Geib
Department of Entomology
Penn State University

The Asian longhorned beetle (ALB) is an invasive species introduced into the U.S. from China. It has a broad host range and has resulted in the loss of thousands of hardwood trees, especially maples. Like other wood-feeding insects, ALB must acquire its nutrition by degrading lignocellulose to obtain nutrients and energy. Ce llulolytic enzymes in the ALB gut may originate from symbionts, the insect itself, or some combination of the two. We surveyed for bacterial and fungal community composition from the gut of mid-instar larval ALB fed in different host tree species using culture independent community analysis. PCR amplification and cloning of the total gut DNA for the 16S rDNA region for bacteria and translation elongation factor-1α region for fungi allowed us to screen for members of the microbial community that differed in insects fed in different host tree species. In larvae fed on sugar maple or pin oak, the gut was found to harbor a rich variety of bacterial and fungal species, including several unique genera (e.g., Cellulosimicrobium sp. and Fusarium sp.) known to play a role in wood decay. Also, the complete suite of cellulolytic enzymes (endo- and exo-glucanases as well as beta-glucosidases) were detected in beetle guts using specific substrates, including an assay that provides direct evidence of lignin degradation. We are collaborating with the DOE's Joint Genome Institute to determine the metagenome sequence of the gut microbe community in ALB. The metagenome sequence should reveal the genes for cellulolytic enzymes in the ALB gut, which may have applications in the conversion of lignocellulose to ethanol.