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The multicomplex cellulase system of Clostridium papyrosolvens and microbial interactions in cellulose biodegradation
Abstract
Cellulose hydrolysis by Clostridium papyrosolvens requires a high-molecular-weight enzyme system. This system was fractionated by means of anion exchange chromatography into at least seven distinct multiprotein complexes with molecular weights ranging from 500,000 to 660,000. Electron microscopy examination revealed distinct ultrastructural features for each complex. Polypeptide composition and enzyme activity profiles varied from complex to complex. CMCase-active protein subunits were present in all of the complexes, but only two of the complexes had xylanase-active subunits. The xylanase specific activity of these two complexes was more than 8-fold higher than that of the unfractionated cellulase preparation. Three of the complexes hydrolyzed crystalline cellulose (Avicel). Experiments involving recombination of the ion exchange chromatography fractions, including the three Avicelase-active complexes, indicated that synergistic interactions occur in the hydrolysis of crystalline cellulose by this enzyme system. All complexes showed high affinity for cellulose. A 125,000 M$\sb{\rm r}$ glycoprotein (S4) which showed similarities to the apparently non-catalytic CipA scaffolding and cellulose-binding protein present in the cellulosome of Clostridium thermocellum was the only polypeptide present in all seven complexes. Purification of S4 was achieved by high performance electrophoresis chromatography, and the N-terminal amino acid sequence, different from that of CipA, was determined. Synthesis of the multicomplex system was inducible. This is the first study demonstrating that more than one multiprotein complex is responsible for hydrolysis of crystalline cellulose and the results emphasize the remarkable structural and functional complexity of the polysaccharide-hydrolyzing systems of anaerobic bacteria. Physiological interactions between cellulolytic bacteria and other bacteria which utilize the hydrolysis products of extracellular bacterial cellulases were investigated. To pursue these studies two strains of a new species of non-cellulolytic, obligately anaerobic, thermophilic spirochete, for which the name Spirochaeta caldaria was proposed, were isolated. S. caldaria was grown in coculture with the thermophilic cellulolytic bacterium C. thermocellum in a medium containing cellulose as the only fermentable substrate. In the coculture cellulose was broken down at a faster rate than in the clostridial monoculture. The results are consistent with the suggestion that interactions between cellulolytic bacteria and non-cellulolytic spirochetes enhance cellulose breakdown in natural environments in which cellulose-containing plant material is biodegraded.
Subject Area
Microbiology|Biochemistry
Recommended Citation
Pohlschroder, Mechthild, "The multicomplex cellulase system of Clostridium papyrosolvens and microbial interactions in cellulose biodegradation" (1994). Doctoral Dissertations Available from Proquest. AAI9420678.
https://scholarworks.umass.edu/dissertations/AAI9420678