title: The complete genome sequence of Fibrobacter succinogenes S85 reveals a cellulolytic and metabolic specialist.
abstract: Fibrobacter succinogenes is an important member of the rumen microbial community that converts plant biomass into nutrients usable by its host. This bacterium, which is also one of only two cultivated species in its phylum, is an efficient and prolific degrader of cellulose. Specifically, it has a particularly high activity against crystalline cellulose that requires close physical contact with this substrate. However, unlike other known cellulolytic microbes, it does not degrade cellulose using a cellulosome or by producing high extracellular titers of cellulase enzymes. To better understand the biology of F. succinogenes, we sequenced the genome of the type strain S85 to completion. A total of 3,085 open reading frames were predicted from its 3.84 Mbp genome. Analysis of sequences predicted to encode for carbohydrate-degrading enzymes revealed an unusually high number of genes that were classified into 49 different families of glycoside hydrolases, carbohydrate binding modules (CBMs), carbohydrate esterases, and polysaccharide lyases. Of the 31 identified cellulases, none contain CBMs in families 1, 2, and 3, typically associated with crystalline cellulose degradation. Polysaccharide hydrolysis and utilization assays showed that F. succinogenes was able to hydrolyze a number of polysaccharides, but could only utilize the hydrolytic products of cellulose. This suggests that F. succinogenes uses its array of hemicellulose-degrading enzymes to remove hemicelluloses to gain access to cellulose. This is reflected in its genome, as F. succinogenes lacks many of the genes necessary to transport and metabolize the hydrolytic products of non-cellulose polysaccharides. The F. succinogenes genome reveals a bacterium that specializes in cellulose as its sole energy source, and provides insight into a novel strategy for cellulose degradation.
authors.affiliation: DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Garret
authors.initials: G
authors.lastname: Suen
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Weimer
authors.forename: David M
authors.initials: DM
authors.lastname: Stevenson
authors.forename: Frank O
authors.initials: FO
authors.lastname: Aylward
authors.forename: Julie
authors.initials: J
authors.lastname: Boyum
authors.forename: Jan
authors.initials: J
authors.lastname: Deneke
authors.forename: Colleen
authors.initials: C
authors.lastname: Drinkwater
authors.forename: Natalia N
authors.initials: NN
authors.lastname: Ivanova
authors.forename: Natalia
authors.initials: N
authors.lastname: Mikhailova
authors.forename: Olga
authors.initials: O
authors.lastname: Chertkov
authors.forename: Lynne A
authors.initials: LA
authors.lastname: Goodwin
authors.forename: Cameron R
authors.initials: CR
authors.lastname: Currie
authors.forename: David
authors.initials: D
authors.lastname: Mead
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Brumm
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D055162:Biocatalysis; D001692:Biological Transport; D002480:Cellulase / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism*; D004950:Esterases / Q000378:metabolism; D045848:Fibrobacter / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D005798:Genes, Bacterial / Q000235:genetics; D016680:Genome, Bacterial / Q000235:genetics*; D006026:Glycoside Hydrolases / Q000378:metabolism; D006868:Hydrolysis; D010802:Phylogeny; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D020543:Proteome / Q000145:classification; D012417:Rumen / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D020543:Proteome; D002482:Cellulose; D004950:Esterases; D006026:Glycoside Hydrolases; C023305:hemicellulase; D002480:Cellulase