Do rumen Bacteroidetes utilize an alternative mechanism for cellulose degradation?

• Published in: mBio Vol. 5; no. 4; pp. e01401 - e01414
• Main Authors: Naas, A E, Mackenzie, A K, Mravec, J, Schückel, J, Willats, W G T, Eijsink, V G H, Pope, P B
• Format: Journal Article
• Language: English
• Published: United States American Society of Microbiology 05.08.2014
• Subjects: Animals; Bacteroidetes - metabolism; Cattle; Cellulose - metabolism; Opinion/Hypothesis; Rumen - microbiology
• ISSN: 2161-2129; 2150-7511
• DOI: 10.1128/mBio.01401-14

Uncultured and therefore uncharacterized Bacteroidetes lineages are ubiquitous in many natural ecosystems which specialize in lignocellulose degradation. However, their metabolic contribution remains mysterious, as well-studied cultured Bacteroidetes have been shown to degrade only soluble polysaccharides within the human distal gut and herbivore rumen. We have interrogated a reconstructed genome from an uncultured Bacteroidetes phylotype that dominates a switchgrass-associated community within the cow rumen. Importantly, this characterization effort has revealed the first preliminary evidence for polysaccharide utilization locus (PUL)-catalyzed conversion of cellulose. Based on these findings, we propose a further expansion of the PUL paradigm and the saccharolytic capacity of rumen Bacteroidetes species to include cellulose, the most abundant terrestrial polysaccharide on Earth. Moreover, the perspective of a cellulolytic PUL lays the foundation for PULs to be considered an alternative mechanism for cellulose degradation, next to cellulosomes and free-enzyme systems.