Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process, which takes place in the front part of the digestive system and therefore is called foregut fermentation, typically requires the fermented ingesta to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word "ruminant" comes from the Latin ruminare, which means "to chew over again".
Cellulase is any of several enzymes produced chiefly by fungi, bacteria, and protozoans that catalyze cellulolysis, the decomposition of cellulose and of some related polysaccharides:
Dictyoglomus is a genus of bacterium, given its own Phylum, called the Dictyoglomi. This organism is extremely thermophilic, meaning it thrives at extremely high temperatures. It is chemoorganotrophic, meaning it derives energy by metabolizing organic molecules. This organism is of interest because it elaborates an enzyme, xylanase, which digests xylan, a heteropolymer of the pentose sugar xylose. By pretreating wood pulp with this enzyme, paper manufacturers can achieve comparable levels of whiteness with much less chlorine bleach.
Endo-1,4-β-xylanase is any of a class of enzymes that degrade the linear polysaccharide xylan into xylose, thus breaking down hemicellulose, one of the major components of plant cell walls:
Fibrobacterota is a small bacterial phylum which includes many of the major rumen bacteria, allowing for the degradation of plant-based cellulose in ruminant animals. Members of this phylum were categorized in other phyla. The genus Fibrobacter was removed from the genus Bacteroides in 1988.
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.
Neocallimastigomycota is a phylum containing anaerobic fungi, which are symbionts found in the digestive tracts of larger herbivores. Anaerobic fungi were originally placed within phylum Chytridiomycota, within Order Neocallimastigales but later raised to phylum level, a decision upheld by later phylogenetic reconstructions. It encompasses only one family.
Cytophaga is a genus of Gram-negative, gliding, rod-shaped bacteria. This bacterium is commonly found in soil, rapidly digests crystalline cellulose C. hutchinsonii is able to use its gliding motility to move quickly over surfaces. Although the mechanism for this is not known, there is a belief that the flagellum is not used
The Xanthobacteraceae are a family of bacteria that includes Azorhizobium, a genus of rhizobia. Xanthobacteraceae bacteria are diverse and Gram-negative, rod-shaped, and may be motile or non-motile depending on the specific bacteria. Their cells range in size from 0.4–1.0 × 0.8–6 µm, but when grown in the presence of alcohol as the sole carbon source, they can reach up to 10 µm in length. These bacteria do not form spores and have opaque, slimy colonies that appear slightly yellow due to the presence of zeaxanthin dirhamnoside.
In molecular biology, Glycoside hydrolase family 10 is a family of glycoside hydrolases.
In molecular biology, glycoside hydrolase family 52 is a family of glycoside hydrolases.
Clostridium aminophilum is a species of gram-positive ammonia-producing ruminal bacteria, with type strain FT.
Pseudobutyrivibrio xylanivorans is a species of butyrate-producing bacteria from the rumen. It is Gram-negative, anaerobic, non-spore-forming, curved rod-shaped and motile by means of a single polar or subpolar flagellum. Its type strain is Mz 5T. xylanivorans means xylan-digesting.
Butyrivibrio hungatei is a species of Gram-negative, anaerobic, non-spore-forming, butyrate-producing bacteria. It is curved rod-shaped and motile by means of single polar or subpolar flagellum and is common in the rumen. Its type strain is JK 615T.
Neocallimastix patriciarum is a species of fungus that lives in the rumen of sheep and other ruminant species. N. patriciarum is an obligate anaerobe and is an important component of the microbial population within the rumen. Only one of a few rumen fungi, this species is interesting and unique within the fungal world. Originally thought to be a flagellate protists, species within the phylum Neocallimastigomycota were first recognized as a fungus by Colin Orpin in 1975 when he demonstrated that they had cell walls of chitin
Pseudobutyrivibrio is a Gram-negative, anaerobic and non-spore-forming bacterial genus from the family of Lachnospiraceae.
Thermomyces lanuginosus is a species of thermophilic fungus that belongs to Thermomyces, a genus of hemicellulose degraders. It is classified as a deuteromycete and no sexual form has ever been observed. It is the dominant fungus of compost heaps, due to its ability to withstand high temperatures and use complex carbon sources for energy. As the temperature of compost heaps rises and the availability of simple carbon sources decreases, it is able to out compete pioneer microflora. It plays an important role in breaking down the hemicelluloses found in plant biomass due to the many hydrolytic enzymes that it produces, such as lipolase, amylase, xylanase, phytase, and chitinase. These enzymes have chemical, environmental, and industrial applications due to their hydrolytic properties. They are used in the food, petroleum, pulp and paper, and animal feed industries, among others. A few rare cases of endocarditis due to T. lanuginosus have been reported in humans.
Methanogens are a group of microorganisms that produce methane as a byproduct of their metabolism. They play an important role in the digestive system of ruminants. The digestive tract of ruminants contains four major parts: rumen, reticulum, omasum and abomasum. The food with saliva first passes to the rumen for breaking into smaller particles and then moves to the reticulum, where the food is broken into further smaller particles. Any indigestible particles are sent back to the rumen for rechewing. The majority of anaerobic microbes assisting the cellulose breakdown occupy the rumen and initiate the fermentation process. The animal absorbs the fatty acids, vitamins and nutrient content on passing the partially digested food from the rumen to the omasum. This decreases the pH level and initiates the release of enzymes for further breakdown of the food which later passes to the abomasum to absorb remaining nutrients before excretion. This process takes about 9–12 hours.
Breznakibacter xylanolyticus is a freshwater gliding bacterium that degrades insoluble particulate xylans and dominates xylan fermentation, particularly in sulfur and methane-rich environments. It is the only species in the genus Breznakibacter. At the time of isolation it was classified in the order Cytophagales on the basis of phenotypic characteristics such as polymer degradation and gliding motility. It has since been reclassified to the order Bacteroidales due to 16s rRNA genome sequence analysis.
Anaeromyces robustus is a fungal microorganism that lives in the gut rumen of many ruminant herbivores such as cows and sheep. Previously thought to be protozoa from their flagellated zoospores, they are biomass degraders, breaking down carbohydrates and plant materials from the food the animal ingests. This fungus, therefore, is anaerobic and lives without oxygen. Gut fungi are dramatically outnumbered by other organisms in the microbiome; they are members of the gut microbiome in ruminants and hindgut fermenters and play a key role in digestion.
