Methanogens in digestive tract of ruminants

Methanogens are a group of microorganisms that can produce methane as a byproduct of their metabolism.They hold an important place in the digestive system of ruminants. The digestive tract of ruminants contain four major parts, they are abomasum, rumen, omasum and reticulum.The food with saliva is first passed to the rumen for breaking them into smaller particles and then it moves to the reticulum where the food is broken into further smaller particles and the indigestable particles are sent back for rechewing and then to rumen.  The majority of the anaerobic microbes assisting the cellulose breakdown occupy the rumen. They initiate the fermentation process.The animal absorbs the fatty acids, vitamins and nutrient content on passing the partially digested food from rumen to omasum which, decreases the pH level and thus initiates the release of enzymes for further break down the food which is later passed to the abomasum that absorbs remaining nutrients before excretion.This process takes about 9–12 hours.

Some of the microbes in ruminant digestive system are:

  • Fibrobacter (Bacteroides) succinogenes is a gram negative, cellulolytic and amylolytic methanogen that produces formates, acetates and succinates.
  • Ruminococcus albus is a cellulolytic, xylanolytic bacterium producing ethanol, hydrogen, carbon di oxide, formates and acetates.
  • Ruminococcus flavefaciens[1] is a cellulolytic, xylanolytic bacteria producing formates, acetates, hydrogen and succinates.
  • Butyrivibrio fibrisolvens[2] is a proteolytic, cellulolytic, xylanolytic microbe producing lactate, butyrate, ethanol, hydrogen, carbon dioxide, formates and acetates.
  • Streptococcus bovis is an amylolytic, major soluble sugar fermenter, proteolytic, microbe resulting in lactate, acetate and formate.
  • Ruminobacter (Bacteroides) amylophilus[3] amylolytic, propionate, proteolytic, organism that forms, formates, acetates and succinates.
  • Prevotella (Bacteroides) ruminocola[4] amylolytic, xylanolytic, propionate, proteolytic, microbe that creates, formates, acetates, succinates and propionate.
  • Succinimonas amylolytica amylolytic, dextrinolytic, bacteria forming acetates and succinates.[5]
  • Selenomonas ruminantium[6] amylolytic, major soluble sugar fermenter, glycerol-utilizing, lactate-utilizing, proteolytic, microbe producing acetates, lactates, hydrogen, carbon dioxides and propionates.
  • Lachnospira multiparus propionate, proteolytic, A microbe that results in production of lactate, ethanol, hydrogen, carbon di oxide, formates and acetates.[7]
  • Succinivibrio dextrinosolvens[8] propionate, dextrinolytic, bacteria forming formates, acetates, lactates and succinates
  • Methanobrevibacter ruminantium methanoic, hydrogen utilizing, archaea involved in the creation of methane
  • Methanosarcina barkeri methanoic, hydrogen utilizing, archaea involved in the creation of methane and carbon dioxide.

References
  1. Rincon, M. T.; Cepeljnik, T.; Martin, J. C.; Barak, Y.; Lamed, R.; Bayer, E. A.; Flint, H. J. (2007). "A Novel Cell Surface-Anchored Cellulose-Binding Protein Encoded by the sca Gene Cluster of Ruminococcus flavefaciens". Journal of Bacteriology. 189 (13): 4774–83. doi:10.1128/JB.00143-07. PMC 1913464. PMID 17468247.
  2. Cotta, M. A.; Hespell, R. B. (1986). "Proteolytic activity of the ruminal bacterium Butyrivibrio fibrisolvens". Applied and Environmental Microbiology. 52 (1): 51–8. PMC 203391. PMID 3524460.
  3. Stackebrandt, Erko; Hippe, Hans (1986). "Transfer of Bacteroides amylophilus to a new Genus ruminobacter gen. nov., nom. Rev. As Ruminobacter amylophilus comb. Nov". Systematic and Applied Microbiology. 8 (3): 204–7. doi:10.1016/S0723-2020(86)80078-9.
  4. Avgustin, G; Wright, F; Flint, H. J. (1994). "Genetic diversity and phylogenetic relationships among strains of Prevotella (Bacteroides) ruminicola from the rumen". International Journal of Systematic Bacteriology. 44 (2): 246–55. doi:10.1099/00207713-44-2-246. PMID 7910475.
  5. M. P. Bryant; et al. (1958), "Bacteroides ruminicola N. Sp. and Succinimonas amylolytica the New Genus and Species: Species of Succinic Acid-Producing Anaerobic Bacteria of the Bovine Rumen", Journal of Bacteriology, 76 (1): 15–23, PMC 290147, PMID 13563384
  6. Nisbet, D. J.; Martin, S. A. (1990). "Effect of Dicarboxylic Acids and Aspergillus oryzae Fermentation Extract on Lactate Uptake by the Ruminal Bacterium Selenomonas ruminantium". Applied and Environmental Microbiology. 56 (11): 3515–8. PMC 185007. PMID 16348354.
  7. D. Dušková and M. Marounek (2001), "Fermentation of pectin and glucose, and activity of pectin-degrading enzymes in the rumen bacterium Lachnospira multiparus", Letters in Applied Microbiology, 33 (2): 159–163, doi:10.1046/j.1472-765x.2001.00970.x
  8. O'Herrin, S. M.; Kenealy, W. R. (1993). "Glucose and carbon dioxide metabolism by Succinivibrio dextrinosolvens". Applied and Environmental Microbiology. 59 (3): 748–55. PMC 202185. PMID 8481001.
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