Studies of the Extracellular Glycocalyx of the Anaerobic Cellulolytic Bacterium
            <i>Ruminococcus albus</i>
            7

Weimer, Paul J.; Price, Neil P. J.; Kroukamp, Otini; Joubert, Lydia-Marié; Wolfaardt, Gideon; Zyl, Willem H. van

doi:10.1128/aem.01632-06

Cited by 41 publications

(32 citation statements)

References 56 publications

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“…In an earlier report (13), transmission electron microscopic visualization of ruthenium red-labeled R. albus cells indicated an extensive "coat" layer, described as a compact mat of polysaccharide fibers external to the cell wall. This polysaccharide coat, or "glycocalyx," was considered in subsequent works to mediate adhesion of the cells to cellulose (14,19). In a later work, it was shown that most of the cellulases and xylanases in R. albus SY3 were associated with the capsular and cell wall fraction but were severely reduced on the surfaces of an adhesion-defective mutant (7).…”

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Cell Surface Enzyme Attachment Is Mediated by Family 37 Carbohydrate-Binding Modules, Unique to Ruminococcus albus

et al. 2008

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The rumen bacterium Ruminococcus albus binds to and degrades crystalline cellulosic substrates via a unique cellulose degradation system. A unique family of carbohydrate-binding modules (CBM37), located at the C terminus of different glycoside hydrolases, appears to be responsible both for anchoring these enzymes to the bacterial cell surface and for substrate binding.Ruminococcus albus is widely recognized as one of the specialist cellulose-degrading bacteria resident in the rumena and gastrointestinal tracts of herbivores. Most isolates have been shown to utilize cellulose, xylan, and cellobiose as carbon sources and found to produce a wide range of enzymatic activities, including ␤-glucosidase, ␤-xylosidase, ␣-galactosidase, ␣-arabinosidase, cellulase, polygalacturonase, and ␤-1,4-xylanase activities (2, 3, 5). Interestingly, many of these glycoside hydrolases bear a recently described family 37 carbohydratebinding module (CBM37), which appears to be exclusive to R. albus. These ϳ100-residue modules were first identified at the C-terminal ends of an exoglucanase (Cel48A) and a processive endocellulase (Cel9B) from R. albus strain 8 (1) and appear to be nondiscriminatory in their carbohydrate-binding properties, recognizing a variety of polysaccharides, including cellulose, xylan, chitin, and lichenan (21). This breadth of adhesive properties makes the CBM37 family unique among the CBM families known to date. A preliminary examination of the draft genome sequence for R. albus strain 8 suggests that CBM37 modules, which are grouped into three major subtypes, are present in numerous R. albus polysaccharide-degrading enzymes and other nonenzymatic proteins from this bacterium (http://blast.jcvi.org/rumenomics/index.cgi).Previous studies have shown that effective cellulose hydrolysis by R. albus strains is conditional on the provision of micromolar concentrations of phenylacetic and phenylpropionic acids (9,17,18). These compounds appear to influence capsule formation by the bacterium, and cellulase activity is retained as high-molecular-mass complexes on the bacterial cell surface. In the absence of phenylacetic and phenylpropionic acids, the adhesion of the bacterium to cellulose (and its hydrolysis) is negatively affected. Additionally, cellulase activity is secreted into the culture medium and, by size exclusion chromatography, is shown to be present in a form suggesting that there is no aggregation of activity into larger, multiprotein complexes (17). Although it was long believed that these characteristics were attributable to a cellulosomal mode of enzyme organization, the identification of CBM37 modules (rather than dockerins) in these two key enzymes suggests that the CBM37 modules might play some role(s) in protein retention to the bacterial cell surface. In the present study, we present evidence to validate this hypothesis, and we propose that an additional function for the CBM37 family is the attachment of the parent protein to the bacterium's cell surface.Three different CBM37 modules from R. albus, C...

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Cell Surface Enzyme Attachment Is Mediated by Family 37 Carbohydrate-Binding Modules, Unique to Ruminococcus albus

et al. 2008

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“…R. albus belongs to the phylum Firmicutes, and like other cellulolytic Firmicutes, employs cellulosomes to adhere to and deconstruct cellulose. R. albus is thought to also employ other cellulose adherence mechanisms, including Pil family proteins (11) and an exopolysaccharide glycocalyx (15). R. albus produces ethanol and CO 2 as its major fermentation products, along with lesser amounts of acetate, formate, and H 2 (13).…”

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Complete Genome of the Cellulolytic Ruminal Bacterium Ruminococcus albus 7

et al. 2011

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“…The consortium of rumen microorganisms may consist of cellulolytic and non‐cellulolytic microorganisms, which collectively accelerate substrate degradation and colonization (Shinkai, Ueki, & Kobayashi, ). We observed extracellular complexes that are synthesized by some species of rumen microorganisms, which are known as appendages or small cellular extensions in Ruminococcus albus and apparently attach bacterial cells to the substrate (Weimer et al., ), concentrating their hydrolytic enzymes in specific sites (Wilson, ). The development of extracellular complexes was highest at 24 hr of Festulolium incubation, which was when the maximum xylanase activity occurred.…”

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Histochemical changes in early and mature Festulolium and maturation's effects on rumen bacteria activity and in vitro degradation

et al. 2018

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The nutritional quality of grasses decreases with maturity due to increases in content of cell wall (CW) and lignified tissue, which affect the degradation and fermentation variables of the grasses. The effect of leaf age and tissue‐microbial attachment during the degradation of Festulolium at 28 and 35 days of regrowth was evaluated in vitro by gas production. Fragments from the middle part of the blade of Festulolium leaves were stained for lignin with phloroglucinol solution, and the lignified area was measured. Subepidermal fibers of the abaxial and adaxial central vein of leaves contributed most to the lignification of Festulolium at 35 days compared with that at 28 days. Variables of gas production and concentrations of volatile fatty acids and ammonia nitrogen were affected by regrowth age. Activity for cellulases (8.19 IU/g dry matter [DM]) was highest between 12 and 16 hr of incubation and for xylanases between 16 and 24 hr (51.09 IU/g DM) without differences between regrowth ages. Scanning electron microscopy showed the following sequence: primary CW degradation started at 12 hr, a large population of microbiota were attached to CWs with extracellular protein complexes at 24 hr, and microbiota were attached to lignified cells at 48 hr. Therefore, during in vitro CW degradation of Festulolium, enzymatic activities increased before microbiota attachment to CWs, which was maintained when xylanase activity declined. Thus, structural analysis conducted using histochemistry and scanning electron microscopy helped to characterize the degradation of plant tissues and the interactions with ruminal microorganisms.

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Studies of the Extracellular Glycocalyx of the Anaerobic Cellulolytic Bacterium Ruminococcus albus 7

Cited by 41 publications

References 56 publications

Cell Surface Enzyme Attachment Is Mediated by Family 37 Carbohydrate-Binding Modules, Unique to Ruminococcus albus

Cell Surface Enzyme Attachment Is Mediated by Family 37 Carbohydrate-Binding Modules, Unique to Ruminococcus albus

Complete Genome of the Cellulolytic Ruminal Bacterium Ruminococcus albus 7

Histochemical changes in early and mature Festulolium and maturation's effects on rumen bacteria activity and in vitro degradation

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