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A Microbial Biorealm page on the genus Neocallimastix


Higher Order Taxa- Eukaryota; Fungi; Neocallimastigaceae; Neocallimastix

Species- N. frontalis, N.hurleyensis, N. joyonii, N. patriciarum, N. variabilis, N. sp. AF-CTS-2G, N.sp. AF-CTS-BF-2, N. sp. GE13, N. sp. GMLF1, N. sp. JB-1999, N. sp. LM-2, N.sp. W-1

Genus: Neocallimastix

Description and Significance

Neocallimastix is an anerobic genus of fungi. Neocallimastix forms a crucial component of the microbial population of the rumen of herbivorous mammals. Neocallimastix contains polyflagellate zoopores and grow on a range of simple and complex carbohydrates in the rumen of sheep and cattle. Neocallimastix is a type of highly fibrolytic microorganism that is capable of colonizing and degrading the major polysaccharides of plant materials (celluloseand hemicellulose) in the rumen ecosystem. This fungus could be exploited for its production of cellulolytic and xylanolytic enzymes. Neocallmstix has been shown to possess diverse plant polysaccharide hydrolase activities, a high capacity for cellulose degradation, and the ability to grow on cellulose as a sole carbohydrate source.


There have been no clear studies surrounding this microbe’s genome.

Cell Structure

Neocallimastix, along with Piromyces, Orpinomyces, Anaeromyces, Caecomyces and the recently described Cyllamyces are anaerobic fungi belonging to the Chytridiomycetes family Neocallimastigacaeae . They are located in the gastrointestinal tract of large herbivorous animals, including cows and sheep. The “gut” fungi are primary colonizer s of plant material in the rumen, and together with rumen bacteria and protozoa, they are responsible for degrading of ingested plant biomass that would be otherwise indigestible to the host animal. The vast repertoire of potent plant cell-wall degrading enzymes secreted by these fungi has been characterized more fully than any other area of their biology. The structure is complex and supramolecular in order for them to degrade ingested plant cell walls. A significant number of these enzymes appear to be the result of trans-kingdom transfer from bacteria. These structures are also responsible for energy generation. . The organelle responsible for energy generation in the absence of any mitochondria, the hydrogenosome, has been used as a model to understand the metabolic processes of obligately anaerobic eukaryotes. Anaerobic fermentation products include ethanol and H2, production of the latter being associated with particular organelles termed hydrogenosomes As a result of these fungi’s extreme nature, little information is available on the genomes. The AT content of the anaerobic fungal genome is approximately 80-85 mol% and is amongst the highest reported in any organism. The nucleotide bias is reflected in both the coding and non-coding regions of the genome, with codon usage tending towards more AT-rich codons. The non-coding regions of the anaerobic fungal genome are known to be extremely AT-rich.

Neocallimastix particulum xylanase NpXyn11A is an anaerobic fungus that is unusual in that it represents one of the rare examples of a fungal GH11 enzyme that is insensitive to XIP-I (wheat protein that acts on fungul but not bacterial GH11 xylanases). Neocallimastix particulum xylanase NpXyn11A displays high catalytic activity. Several conclusions have been drawn to determine the high catalytic activity. The enhanced activity of the enzyme is a result of its crystal structure of the apo form (enzyme receptor in its free state without substrates or inhibitors bound) which revealed the presence of both -3 and +3 subsites. Also, it has a pH optimum of 7.5 and a ∆G of -2.1 kcal/mol which may also contribute to enhanced activity of the enzyme.

Life Cycle

The fungi of the genus Neocallimastic have a simple life-cycle alternating between a motile multi-flagellate zoospore and an extensive vegetative stage usually found associated with particulate plant material in the alimentary tract. They have been assigned to a new family, the Neocallimasticaceae, in the order Spizellomycetales of the Chytridiomycetes but their exact taxonomic affinities are uncertain.


Evolutionarily, this genus is important because they lack one of the most important organelles involved in supplying ATP. Instead of mitochondria they have something called hydrogenosomes which also supply ATP but also produce hydrogen concurrently. Past studies have found a high probability between of hydrogenosomes and mitochondria evolving from the same organelle because they share a common ADP/ATP exchange pathway.


The habitat that Neocallimastix thrives in includes the anaerobic environment of rumen in ruminants, murine intestines, and possibly environmental organisms. Neocallimastix is a Chytrid fungus. Neocallimastix ferments the sugars that reach the rumens of ruminants and murines to break them down into lactate, ethanol, formate, and hydrogen. It is currently not known how extensively this fungus breaks down the cellulose in the environment. It has a contribution to all the other living microbes located in the rumen in order to break down cellulose into digestible material.

Current Research

Generally, current research is focusing on the specialized organelles of these microbes as well as their physiological characteristics. The Journal of Applied Microbiology recently published an article studying the importance of aromatic amino acids and comparing that with phenyl acids in order to determine optimal xylan fermentation. Another study was published by Archives of Animal Nutrition that looked into how anaerobic fungi in smaller ruminants break down wheat finding that without these fungi digestion exponentially decreases. An additional recent study by the Faculty of Agriculture at Ümam University found that when utilizing glucose as an energy source Neocallimastix enzymatic activity drastically decreases compared to Xylan and Avicel.


Arora, D (1991). Handbook of Applied Mycology. Marcel Dekker, Retrieved 12/7/2008, from id=I_hqPQTUf3cC&printsec=frontcover

Carroll, G (1992). The fungal community: Its organization and role in the ecosystem.. Marcel Dekker, Retrieved 12/7/2008, from

Denman, S. et al (1996). Characterization of a Neocallimastix patriciarum Cellulase cDNA (celA) Homologous to Trichoderma reesei Cellobiohydrolase II. Appliedand Environmental Microbiology. 1889-1896.

Ekιncι, M., Özköse, E., & Akyol, İ. (2006, September). Effects of Sequential Sub-Culturing on the Survival and Enzyme Activity of Neocallimastix hurleyensis. Turkish Journal of Biology, 30(3), 157-162. Retrieved December 7, 2008, from Academic Search Premier database.

Fenchel, T (1995). Ecology and evolution in anoxic worlds. Oxford University Press, Retrieved 12/07/2008, from web&ots=izf46rzewu&sig=EM8FJNuFZWOf8k0va11nJZt1cd4&sa=X&oi=book_result&resnum=2&ct=result#PPP1,M1.

Fligerova Katerina, Pazoutova Sylva, Hodrova Blaka. (1998). Molecular Genotypic of Rumen Fungi Based on RFLP Analysis. Scientific Symp. Animal Microbiology. 72, 95-98.

Giezen, M., Slotboom, D. J., Horner, D. S., Dyal, P. L., Harding, M., Xue, G., Embley, T. M.,& Kunji, E. R. S. (2002). Conserved properties of hydrogenosomal and mitochondrial ADP/ATP carriers: a common origin for both organelles. European Molecular Biology Organization. 21, 572-579.

Guliye, A., & Wallace, R. (2007, October). Effects of aromatic amino acids, phenylacetate and phenylpropionate on fermentation of xylan by the rumen anaerobic fungi, Neocallimastix frontalis and Piromyces communis. Journal of Applied Microbiology, 103(4), 924-929. Retrieved December 7, 2008, doi:10.1111/j.1365-2672.2007.03327.x

Lockhart, R. J., Van Dyke, M. I., Beadle, I. R., Humphreys, P., & McCarthy, A. J. (2006). Molecular Biological Detection of Anaerobic Gut Fungi (Neocallimastigales) from Landfill Sites. American Society for Microbiology. 72, 5659–5661.

Nicholson Matthew J., Theodorou Michael K., BrookmanvJayne L.(2005). Molecular analysis of the anaerobic rumen fungus Orpinomyces – insights into an AT-rich genome.microbiology 121-133

Scupham, AJ (2006). Abundant and diverse fungal microbiota in the murine intestine. Applied Environmental Microbiology, 72.

Srinivasan, K. et al (2001). Efficient production of cellulolytic and xylanolytic enzymes by the rumen anaerobic fungus, Neocallimastix frontalis, in a repeated batch culture. Journal of Bioscience and Bioengeneering.91(2), 153-158.

Thareja, A., Puniya, A. K., Goel, G., Nagpal, R., Sehgal, J. P., Singh, P. H. & Singh, K. (2006). In vitro degradation of wheat straw by anaerobic. Archives of Animal Nutrition. 60, 412-417.

Vardakou Maria, Dumon Claire, Murray James W1, Christakopoulos Paul, Weiner David P., Juge Nathalie, Lewis Richard J., Gilbert Harry J., Flint James E (2008) Understanding the Structural Basis for Substrate and Inhibitor Recognition in Eukaryotic GH11 Xylanases. Journal of Molecular Biology 375, 1293-1305.

Edited by student of Dr. Kirk Bartholomew