**Abstract**

To elucidate the microbial dynamics inside rumen of animals of livestock importance and to provide a better ration to them in order to control various metabolic disorders, a better understanding of the rumen microbial ecology is pivotal. The fundamental knowledge of methanogenic population inside gut environment and ruminal fermentation is of considerable importance as it has a significant impact on the various metabolic activities of the animal. The major methanogens isolated and characterized from ruminants like cattle, sheep, steers, goats, reindeers are from the order *Methanobacteriales*, *Methanomicrobiales*, *Methanococcales*, *Methanosarcinales* and *Methanomassiliicoccales*. The chapter deals with present knowledge available regarding the methanogenic diversity present in the gastrointestinal tract of ruminants all over the world primarily through constructing 16S rRNA gene clone libraries and tries to uncover the new genera in ruminant's microbiome and their adaptations in extreme environment. To get a better idea regarding the composition of methanogen community, further studies are required in relation to the effect of diet and animal species to the rumen methanogens.

**Keywords:** *Archaea*, gut, methanogens, microbiome, *Methanobrevibacter* spp., rumen

## **1. Introduction**

The methanogens are one of the primitive life forms on earth which have evolved to be able to thrive in extreme harsh temperatures (severe hot and cold) and living conditions (salt and pH) uninhabitable for most of other life forms. Although a vast proportion of methanogens are *Archaea* but protists like algae, fungi and protozoa also form a diversity of this group. Besides their anthropogenic existence, methanogens are present in a wide area of ecological niches ranging from peat bogs to deep sea sediments and hydrothermal vents and hot springs [1, 2].

The large number of microbial population in natural anaerobic systems remains unexplored as enumeration techniques like selective enrichment, pure-culture Isolation, most-probable number estimates are time consuming and labor intensive. Culture less approaches has allowed deciphering the diversity of microbial community thriving across wide environmental ranges. Various anaerobic culture

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*Extremophilic Microbes and Metabolites - Diversity, Bioprospecting and Biotechnological...*

estacionales de la biomasa microbiana en las principales especies de dos tipos de bosques tropicales. Multiciencias.

[26] Dijkman NA, Boschker HT, Stal LJ, Kromkamp JC. Composition and heterogeneity of the microbial community in a coastal microbial mat as revealed by the analysis of pigments and phospholipid-derived fatty acids. Journal of Sea Research.

[27] Muyzer G, Stams AJ. The ecology and biotechnology of sulphate-reducing bacteria. Nature Reviews Microbiology.

[28] Waldrop MP, Balser TC, Firestone MK. Linking microbial community composition to function in a tropical soil. Soil Biology and Biochemistry.

[29] Richardson AE, Simpson RJ. Soil microorganisms mediating phosphorus

[30] George E, Marschner H, Jakobsen I. Role of arbuscular mycorrhizal fungi in uptake of phosphorus and nitrogen from soil. Critical Reviews in Biotechnology. 1995;**15**(3-4):257-270

[31] Wu QS, Zou YN, He XH. Differences of hyphal and soil phosphatase activities

in drought-stressed mycorrhizal trifoliate orange (*Poncirus trifoliata*) seedlings. Scientia Horticulturae.

availability update on microbial phosphorus. Plant Physiology.

2004;**4**(2):96-103

2010;**63**(1):62-70

2008;**6**(6):441

2000;**32**(13):1837-1846

2011;**156**(3):989-996

2011;**129**(2):294-298

[17] Medina E, Cuevas E. Propiedades fotosintéticas y eficiencia de uso de agua de plantas leñosas del bosque deciduo de Guánica: Consideraciones generales y resultados preliminares. Acta Científica.

[18] Govender Y, Cuevas E, Sternberg LD, Jury MR. Temporal variation in stable isotopic composition of rainfall and groundwater in a tropical dry forest in the northeastern Caribbean. Earth

[19] Gee GW, Bauder JW. Particle-Size Analysis 1. Soil Science Society of America. Madison, Wl USA: American

[20] Anderson J, Ingram J. Tropical Soil Biology and Fertility (TSBF): Handbook of Methods. Wallingford, Ox UK: CAB

[21] Schutter ME, Dick RP. Comparison of fatty acid methyl ester (FAME) methods for characterizing microbial communities. Soil Science Society of America Journal. 2000;**64**(5):1659-1668

[22] Cuevas E, Medina E. Nutrient dynamics within Amazonian forests. Oecologia. 1988;**76**(2):222-235

[23] Pérez-Harguindeguy N, Díaz S, Cornelissen JH, Vendramini F, Cabido M, Castellanos A. Chemistry and toughness predict leaf litter decomposition rates over a wide spectrum of functional types and taxa in Central Argentina. Plant and Soil.

[24] Schneider T, Keiblinger KM, Schmid E, Sterflinger-Gleixner K, Ellersdorfer G, Roschitzki B, et al. Who is who in litter decomposition? Metaproteomics reveals major microbial players and their biogeochemical functions. The ISME Journal. 2012;**6**(9):1749

[25] Tremont O, Cuevas E. Carbono orgánico, nutrientes y cambios

Interactions. 2013;**17**(27):1-20

Society of Agronomy; 1986

International; 1993

2000;**218**(1-2):21-30

1990;**4**:25-36

techniques led to the discovery of a third microbial kingdom, the *Archaebacteria*, which includes methanogens [3, 4]. Further the target specific sequence analysis of 16S rRNA gene in 1970's had redefined taxonomy of all living organisms into three main domains. Methanogens belong to the 3rd domain of life-*Archaea*, other two being—*Eucarya* and *Bacteria*. *Archaea* is further divided into phylums *Crenarchaeota* and *Euryarchaeota* [5].
