Steven W. Hutcheson

Professor

Research Interests: Genetics of microbial pathogenesis; role and regulation of type III protein secretion systems; microbial genomics.

RESEARCH OF THE HUTCHESON LAB

Lignocellulosic biomass is mostly composed of carbohydrate polymers that can be degraded to their constituent sugars if cost effective means can be developed.  These sugars or sugar derivatives can then be turned into various fuels and other specialty chemicals through fermentation.  The limitations in current pretreatments and enzymes necessitate a search for new methods to release these sugars. 

The saprophytic marine bacterium Saccharophagus degradans is capable of enzymatically releasing sugars from many complex polysaccharides using unique mechanisms.  This bacterium is from the Chesapeake Bay and has multiple unusual carbohydrase systems and the accompanying genetic systems.  Thus this bacterium is a repository for unique enzymes and mechanisms for processing complex polysaccharides.  We are studying the novelties of several of the carbohydrase systems produced by this bacterium that are most applicable to biofuel production to provide new tools and techniques.

The approach is to use modern molecular genetics to answer: how does this bacterium eat?    This is not a simple question as this bacterium eats by dissolving complex polysaccharides while in an infinitely large dilutant called the ocean.   Thus it must have mechanisms to vector carbon back to itself.  To help us in this quest, the bacterium has a known genome sequence with a tentative annotation for the genes and their products.  We are using molecular cloning and directed expression to understand the biochemical function of many of the gene products.  The transcriptome has been analyzed using deep sequencing (sequencing of the mRNA present in the cell) so that relative expression of a gene under specific growth conditions can be estimated and regulatory information in promoters deduced.  We have also used quantitative RT-PCR in this application.   The proteome has been analyzed in part by 2 dimensional SDS-PAGE and tandem MS-MS.   Understanding how this bacterium senses the presence of a complex polysaccharide to regulate target genes in another major thrust of this work.  This latter work is being facilitated through the use of comparative genomics with other similar cellulolytic bacteria.  Thus we are using sophisticated, state-of-the-art techniques to understand how these enzyme systems operate. 

We are also working with faculty and students in the Department of Materials Science and Engineering to understand the mechanisms by which organic liquids interact with cellulose during pretreatments.  This work should help reduce the cost of digesting biomass as less enzyme should be required to release sugars from biomass if the right conditions can be established during the pretreatment.

Selected Recent Publications: