Project description:Background (Pseudo)Bacteroides cellulosolvens is a cellulolytic bacterium producing the most extensive and intricate cellulosomal system known in nature. Recently, an elaborate architecture of B. cellulosolvens cellulosomal system was revealed from its genome sequence analysis, and first evidence on the interactions between its structural and enzymatic components were detected in vitro. Yet, the cellulolytic potential of the bacterium in carbohydrate deconstruction may reside only within complete high-molecular weight protein complexes, which are secreted from the bacterium. Results The current proteome-wide work reveals patterns of protein expression of various cellulosomal components, and explores the differential expression signature upon bacterial growth two carbon sources, either cellobiose or microcrystalline cellulose. Mass spectrometry analysis of the bacterial secretome fraction revealed the expression of 24 scaffoldin structural units and 166 dockerin-bearing enzymes, in addition to free enzymatic subunits. All these components comprise cell-free and cell-bound cellulosomes for more efficient carbohydrate degradation. Various glycoside hydrolase (GH) family memebers were represented among 102 carbohydrate-degrading enzymes, including the most abundant GH48 exoglucanase. Specific cellulosomal components were associatred with different carbon sources, in cellulosomal fractions of different molecular weights. Overall, microcrystalline cellulose-derived cellulosomes showed higher expression levels of the structural and enzymatic components, and exhibited the highest degradation activity on five different carbohydrates. The cellulosomal activity of B. cellulosolvens showed high degradation rates that are very promising in biotechnological terms and were compatible with the activity levels exhibited by C. thermocellum purified cellulosomes. Conclusions The current research demonstrates the involvement of key cellulosomal factors participating in the mechanism of carbohydrate degradation by B. cellulosolvens. The powerful ability of the bacterium to exhibit different degradation strategies of various carbon sourcesis revealed. Thus, a novel components reservoir of degradation machineries that may serve for subsequent cellulosomal research, as a pool for designing new cellulolytic cocktails for biotechnological purposes.
