|Van Zyl, W|
Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/27/2003
Publication Date: 5/23/2004
Citation: Weimer, P.J., Kroukamp, O., Joubert, L.M., Wolfaardt, G.M., Van Zyl, W.H. 2004. Characterization of the glycocalyx of cellulose-grown ruminococcus albus. [abstract]. 104th General Meeting of the American Society for Microbiology. B-428. Interpretive Summary:
Technical Abstract: Anaerobic cellulolytic bacteria are thought to adhere to cellulose via several mechanisms, one of which is the production of a glycocalyx containing extracellular polymeric substances (EPS). As the composition and structure of these glycocalyces have not been elucidated, a combination of scanning electron microscopy and chemical analysis was used to characterize the glycocalyx of Ruminococcus albus strain 7. Cultures grown on cellulose fibers displayed preferential degradation within crevices along the fiber axis, but not at the cut ends of fibers. Growth was accompanied by formation of thin cellular extensions that adhered to cellulose, and which formed a ramifying network that interconnected individual cells to one another and to the unraveling cellulose microfibrils. Extraction of whole cultures (grown for 30 or 48 h) with 0.1 N NaOH released carbohydrate and protein in a ratio of 1:5. Treatment of adherent cells with a detergent solution at pH 7 removed almost all of the cells without removing the network of adhering noncellular material. Subsequent treatment of this residue (cellulose plus glycocalyx, C+G) with 2 N trifluoroacetic acid (120 oC, 90 min) resulted in complete removal of the glycocalyx. This treatment released primarily glucose (derived largely from partially degraded cellulose), along with substantial amounts of xylose and mannose (two sugars not typically associated with bacterial glycocalyces) but only traces of galactose (the primary sugar associated with the Clostridium thermocellum cellulosome). Separate extraction of C+G with 0.1 N NaOH resulted in removal of both carbohydrate and protein in a ratio of ~10:1, suggesting that the EPS contained little protein. Calculations, based on the amount of carbohydrate and protein removed by these treatments, indicate that the energetic demands of EPS synthesis for this organism depend on the extent of incorporation of partially degraded cellulose into the EPS. However, in all cases these represent only a small fraction (2 to 4%) of the anabolic ATP expenditure of the culture.