CO-LOCALIZATION AND DISPOSITION OF CELLULOSOMES IN CLOSTRIDIUM CLARIFLAVUM AS REVEALED BY CORRELATIVE SUPER-RESOLUTION IMAGING

Cellulosomes are highly complex nanomachineries capable of plant cell wall hydrolysis. These multi-enzyme complexes are extremely efficient and are produced by specialized anaerobic bacteria which utilize the oligosaccharides released from the breakdown of plant cell wall polysaccharides. Clostridium clariflavumis one of a limited number of known thermophiles that produce cellulosomes. Studies of the interactions among the various components of its cellulosome revealed an intricate system that can be assembled in many different compositions, which includes the largest cellulosome complex known in nature. This complex can contain 160 polysaccharide-degrading enzymes. We explored the disposition of the highly structured, four-tiered cell-anchored cellulosome complex of this bacterium, whereby four separate, integral cellulosome components were subjected to immunolabeling. Imaging of the cells by correlating 3D super-resolution fluorescence microscopy revealed that some of the protuberance-like structures on thecell surface represent cellulosomes and that the components are highly colocalized and organized by a defined hierarchy on the cell surface. The display of the cellulosome on the cell surface was found to differ between cells grown on soluble or insoluble substrates. Cell growth on microcrystalline cellulose and wheat straw exhibited dramatic enhancement in the amount of cellulosomes displayed on the bacterial cell surface.