Molecular basis of an agarose metabolic pathway
acquired by a human intestinal symbiont
, Julie M. Grondin
, Carolyn Amundsen
, Leeann Klassen
, Paul E. Moote
, Yao Xiao
, Nicholas A. Pudlo
, Anuoluwapo Anele
, Eric C. Martens
, G. Douglas Inglis
Richard E.R. Uwiera
, Alisdair B. Boraston
& D. Wade Abbott
In red algae, the most abundant principal cell wall polysaccharides are mixed galactan agars,
of which agarose is a common component. While bioconversion of agarose is predominantly
catalyzed by bacteria that live in the oceans, agarases have been discovered in micro-
organisms that inhabit diverse terrestrial ecosystems, including human intestines. Here we
comprehensively deﬁne the structure–function relationship of the agarolytic pathway from
the human intestinal bacterium Bacteroides uniformis (Bu) NP1. Using recombinant agarases
from Bu NP1 to completely depolymerize agarose, we demonstrate that a non-agarolytic Bu
strain can grow on GAL released from agarose. This relationship underscores that rare
nutrient utilization by intestinal bacteria is facilitated by the acquisition of highly speciﬁc
enzymes that unlock inaccessible carbohydrate resources contained within unusual poly-
saccharides. Intriguingly, the agarolytic pathway is differentially distributed throughout
geographically distinct human microbiomes, reﬂecting a complex historical context for
agarose consumption by human beings.
Department of Biochemistry and Microbiology, University of Victoria, PO Box 3055 STN CSC, Victoria, BC V8W 3P6, Canada.
Agriculture and Agri-Food
Canada, Lethbridge Research and Development Centre, Lethbridge, AB T1J 4B1, Canada.
Department of Agricultural, Food and Nutritional Science,
University of Alberta, Edmonton, AB T6G 2P5, Canada.
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor,
MI 48109 USA. These authors contributed equally: Benjamin Pluvinage, Julie M. Grondin. These authors jointly supervised this work: Alisdair B. Boraston, D.
Wade Abbott. Correspondence and requests for materials should be addressed to A.B.B. (email: firstname.lastname@example.org)
or to D.W.A. (email: email@example.com)