ELUCIDATING THE ARCHITECTURAL ORGANIZATION AND DIVERSITY OF THE PSEUDOBACTEROIDES CELLULOSOLVENS DISCRETE CELLULOSOME

In the bacterial world there are many ways of carbon source utilization, which can lead to the production of ethanol as an alternative source of bioenergy. Cellulosic biomass is an abundant raw material and important feedstock for ethanol production, which is derived from non-food sources such as trees, grasses and all kinds of cellulosic wastes. Consequently, there is an opportunity to utilize cellulosic wastes from different existing industries as an alternative added-value source for biofuel production. Some anaerobic bacteria produce extracellular multi-enzyme systems, highlighted by the cellulosome complex, for degradation of plant cell wall polysaccharides and cellulosic wastes. Such bacteria can produce prodigious numbers of different enzyme components capable of degrading complex polysaccharides. One of the major advantages of the cellulosome-producing bacteria is their ability to degrade different types of complex sugars contained in mixed types of biomass. The organization of enzymes into a cellulosome is considered to concentrate and position them in suitable orientation, both with respect to each other and to the cellulosic substrate for efficient decomposition of the insoluble intractable substrate. Moreover, the fact that the complex is attached to the substrate, on the one hand, and the cell, on the other, results in a minimal diffusion loss of enzymes and hydrolytic products, the latter of which are taken up by the cells thus precluding their inhibition of the cellulolytic enzymes. My research concentrates on one of these bacteria- Pseudoacteroides cellulosolvens which is an anaerobic, mesophilic, cellulolytic bacterium capable of utilizing cellulose and cellobiose as a carbon source. Recently we have sequenced the P. cellulosolvens genome, and subsequent bioinformatic analysis revealed an incredible number of cellulosome-related components, including 78 cohesin modules scattered among 31 scaffoldins and more than 200 dockerin-bearing ORFs. In terms of numbers, this potentially represents the most intricate, compositionally diverse cellulosome system yet known in nature. P. cellulosolvens has a unique cellulosome organization comparative to other bacteria. We focused on revealing the architecture of the cellulosomal structure by examining numerous interactions between cohesin and dockerin modules. Our results demonstrated the architectural organization and sequence diversity of the P. cellulosolvens cellulosomal components and thus provide the molecular basis for future understanding of the potential for a wide array of cohesin-dockerin specificities. Deep understanding of the interactions among cellulosomal components will enable us to design high-efficiency cellulosomes for conversion of plant-derived cellulosic biomass and improved production of biofuels.