Cellulosomes are multi-enzyme extracellular complexes. Cellulosomes are associated with the cell surface and mediate cell attachment to insoluble substrates and degrade them to soluble products which are then absorbed. Cellulosome complexes are intricate, multi-enzyme machines, produced by many cellulolytic microorganisms. They are produced by microorganisms for efficient degradation of plant cell wall polysaccharides, notably cellulose, the most abundant organic polymer on Earth. The multiple subunits of cellulosomes are composed of numerous functional domains that interact with each other and with the cellulosic substrate. One of these subunits, a large glycoprotein "scaffoldin", is a distinctive class of non-catalytic scaffolding polypeptides. The scaffoldin subunit selectively integrates the various cellulases and xylanase subunits into the cohesive complex, by combining its cohesin domains with a typical dockerin domain present on each of the subunit enzymes. The scaffoldin of some cellulosomes, an example being that of Clostridium thermocellum, contains a carbohydrate-binding module that adheres cellulose to the cellulosomal complex.
Acetivibrio thermocellus is an anaerobic, thermophilic bacterium. A. thermocellusm has garnered research interest due to its cellulolytic and ethanologenic abilities, being capable of directly converting a cellulosic substrate into ethanol by consolidated bioprocessing. This makes it useful in converting biomass into a usable energy source. The degradation of the cellulose is carried out in the bacterium by a large extracellular cellulase system called a cellulosome, which contains nearly 20 catalytic subunits. The cellulase system of the bacterium significantly differs from fungal cellulases due to its high activity on crystalline cellulose, being able to completely solubilize crystalline sources of cellulose, such as cotton. However, there are some shortfalls in applying the organism to practical applications due to it having low ethanol yield, at least partially due to branched fermentation pathways that produce acetate, formate, and lactate along with ethanol. There is also evidence of inhibition due to the presence of hydrogen and due to agitation. Some recent research has been directed to optimizing the ethanol-producing metabolic pathway in hopes of creating more efficient biomass conversion.
Thermoanaerobacter is a genus in the phylum Bacillota (Bacteria). Members of this genus are thermophilic and anaerobic, several of them were previously described as Clostridium species and members of the now obsolete genera Acetogenium and Thermobacteroides
Armatimonadota is a phylum of gram-negative bacteria.
Clostridium phytofermentans is an obligately anaerobic rod-shaped spore-forming, Gram-positive bacterium in the family Lachnospiraceae. It is a model organism of interest for its ability to ferment diverse plant polysaccharides including cellulose, hemicellulose, and pectin to ethanol, acetate, and hydrogen. The C. phytofermentans 4.8 Mb genome has been fully sequenced, revealing it contains over 170 enzymes in the CAZy database, though one hydrolase appears to be essential for degrading cellulose.
Caldicellulosiruptor bescii is a species of thermophilic, anaerobic cellulolytic bacteria. It was isolated from a geothermally heated freshwater pool in the Valley of Geysers on the Kamchatka Peninsula in Russia in 1990. The species was originally named Anaerocellum thermophilum, but reclassified in 2010, based on genomic data.
Ruminiclostridium cellobioparum is a species of anaerobic cellulose-degrading Gram-positive bacterium found in the bovine rumen belonging to the family Oscillospiraceae.
Sulfobacillus acidophilus is a species of moderately thermophilic mineral-sulphide-oxidizing bacteria. It is Gram-positive, acidophilic and ferrous-iron-oxidising as well.
Clostridium cellulovorans is an anaerobic, mesophilic, spore-forming cellulolytic bacterium. Its cells are gram-negative and are non-motile rods which form oblong spores. The type strain is 743B. Its role as an object of study is based on the latter notion.
Thermoclostridium stercorarium is a cellulolytic thermophilic bacterium. It is anaerobic, spore-forming and saccharoclastic, with cells being rod-shaped and 0.7 to 0.8 by 2.7 to 7.7 µm in size. Its genome has been sequenced.
Clostridium paradoxum is a moderately thermophilic anaerobic alkaliphile bacteria. It is motile with 2-6 peritrichous flagella and forms round to slightly oval terminal spores. Its type strain is JW-YL-7.
Acetivibrio aldrichii is a Gram-positive, anaerobic, mesophilic, spore-forming and motile bacterium from the genus Acetivibrio.
Acetivibrio alkalicellulosi is an obligately alkaliphilic and anaerobic bacterium from the genus Acetivibrio which has been isolated from sediments of the Beloe soda lake from Buryatiya in Russia.
Thermoclostridium caenicola is a Gram-positive anaerobic bacterium from the genus Thermoclostridium which has been isolated from methanogenic sludge.
Clostridium chartatabidum is a strictly anaerobic and spore-forming bacterium from the genus Clostridium which has been isolated from an ovine rumen in New Zealand.
Acetivibrio clariflavus is an anaerobic bacterium from the genus Acetivibrio which has been isolated from sludge from a cellulose-degrading bioreactor in Japan.
Peptacetobacter hiranonis is a Gram-positive, cellulolytic and motile bacterium from the family Peptostreptococcaceae which has been isolated from human faeces in Okinawa in Japan.
Ruminiclostridium hungatei is an obligately anaerobic, cellulolytic, mesophilic and nitrogen fixing bacterium from the genus of Clostridium which has been isolated from soil in Amherst in the United States.
Cytophagales is an order of non-spore forming, rod-shaped, Gram-negative bacteria that move through a gliding or flexing motion. These chemoorganotrophs are important remineralizers of organic materials into micronutrients. They are widely dispersed in the environment, found in ecosystems including soil, freshwater, seawater and sea ice. Cytophagales is included in the Bacteroidota phylum.
The Ignavibacteriales are an order of obligately anaerobic, non-photosynthetic bacteria that are closely related to the green sulfur bacteria.
