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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Cell Wall Biology and Utilization Research » Research » Publications at this Location » Publication #292970
Title: Unique aspects of fiber degradation by the ruminal ethanologen Ruminococcus albus 7 revealed by physiological and transcriptomic analysis

Author
item CHRISTOPHERSON, MELISSA - University Of Wisconsin
item DAWSON, JOHN - University Of Wisconsin
item Stevenson, David
item CUNNINGHAM, ANDREW - University Of Wisconsin
item BRAMHACHARYA, SHANIT - University Of Wisconsin
item Weimer, Paul
item KENDZIORSKI, CHRISTINA - University Of Wisconsin
item SUEN, GARRET - University Of Wisconsin

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2014
Publication Date: 12/16/2014
Publication URL: http://handle.nal.usda.gov/10113/60089
Citation: Christopherson, M.R., Dawson, J., Stevenson, D.M., Cunningham, A., Bramhacharya, S., Weimer, P.J., Kendziorski, C., Suen, G. 2014. Unique aspects of fiber degradation by the ruminal ethanologen Ruminococcus albus 7 revealed by physiological and transcriptomic analysis. Biomed Central (BMC) Genomics. DOI: 0.1186/1471-2164-15-1066.

Interpretive Summary: Ruminococcus albus is an important fiber-degrading bacterium in the rumen of cattle, sheep, and goats. In order to understand how this bacterium degrades fiber so well, we have obtained the complete DNA sequence of the organism and have used this information to reveal the strategy the organism uses to degrade cellulose and other plant fibers. Surprisingly, this bacterium lacks a cellulosome, the main structure used by most cellulose-degrading anaerobic bacteria, but instead produces a very diverse array of cell-associated enzymes. This information will be useful to researchers who are engineering new processes for conversion of plant biomass to fuels and chemicals.

Technical Abstract: Bacteria in the genus Ruminococcus are important and ubiquitous members of mammalian guts. In particular, ruminococci are key contributors to the rumen ecosystem because they are capable of digesting a wide range of plant cell wall polysaccharides. In bovines, Ruminococcus albus 7 is a primary cellulose degrader that ferments acetate, a nutrient usable by its host. Moreover, it is one of the few organisms that ferments cellulose to ethanol at mesophilic temperatures in vitro. The mechanism of cellulose degradation by R. albus 7 is not well-defined and is thought to involve pilin-like proteins, unique carbohydrate-binding domains, a thick glycocalyx, and cellulosomes. We compared the genome sequence for R. albus 7 with other Clostridiales known to utilize cellulosomes, in addition to other non-fibrolytic clostridia. We found that R. albus 7 does not encode for cellulosomal components. We further probed the fibrolytic capabilities of R. albus 7 using a combination of fermentation analyses and RNA-seq-based transcriptomics. We found that R. albus 7 is capable of fermenting a wide range of fibrous substrates into ethanol. When grown on cellulose in a chemostat, R. albus 7 utilized a carbohydrate-degrading strategy that involves overexpression of the rare CBM37 domain and the tryptophan biosynthetic operon. Our findings contribute to the understanding of carbohydrate degradation by this organism, which may enhance industrial cellulose fermentation efforts, in addition to providing insight into the role of ruminococci as key members of the mamalian gut microbiota.