Ecology and characteristics of methanogenic archaea in animals and humans

Abstract

In this review, the molecular techniques used in animal-based-methanogen studies will be discussed along with how methanogens interact not only with other microorganisms but with their animal hosts as well. These methods not only indicate the diversity and levels of methanogens, but also provide insight on their ecological functions. Most molecular techniques have been based on either 16S rRNA genes or methyl-coenzyme M reductase, a ubiquitous enzyme in methanogens. The most predominant methanogens in animals belong to the genus Methanobrevibacter. Besides methanogens contributing to overall H2 balance, methanogens also have mutual interactions with other bacteria. In addition to shared metabolic synergism, the host animal retrieves additional energy from the diet when methanogens are co-colonized with other normal flora. By comparing genes in methanogens with other bacteria, possible gene transfer between methanogens and other bacteria in the same environments appears to occur. Finally, diets in conjunction with the genetics of methanogens and hosts may represent the biological framework that dictate the extent of methanogen prevalence in these ecosystems. In addition, host evolution including the immune system could serve as an additional selective pressure for methanogen colonization.

Salmonella Pathogenicity and Host Adaptation in Chicken-Associated Serovars

“…Particularly in the lower GIT of monogastric animals (colon or cecum) and the foregut (rumen) of ruminants, microbial populations consist of large numbers of mostly saccharolytic anaerobic microorganisms along with methanogenic archaea, which together result in a highly reduced ecosystem with minimal oxygen (318,320,(352)(353)(354)(355)(356)(357)(358)(359). Given the complexity of diets in general and the recalcitrant nature of some of the fibercontaining components (particularly those consumed by herbivores), the GIT microbial consortia are characterized not only by their anaerobic physiology but also by their ability to hydrolyze fiber polymers into soluble carbohydrates that are readily fermentable (360-364).…”

Temporal analysis of the effect of extruded flaxseed on the swine gut microbiota

“…The composition of the gut microbiota depends on several environmental factors, with diet being among the most important (Ley et al 2008). While Bacteria are the predominant and best characterized members of the swine gut microbiota, Archaea, in the form of methanogens, are also an important component of this microbial ecosystem, since they produce methane (CH 4 ) by oxidizing hydrogen and reducing carbon dioxide and other single-carbon molecules (Saengkerdsub and Ricke 2014). Although methane production in the gut represents a minor energy loss (0.6%-1.3%) in swine, it is a greenhouse gas of environmental concern with growing pigs producing up to 6.5 L CH 4 ·day −1 (Monteny et al 2001;Jørgensen et al 2007).…”

Methanogens in the Environment: An Insight of Methane Yield and Impact on Global Climate Change

“…The unceasing improvement of molecular methods for this study of environmental microorganisms has facilitated the characterization of methanogens community. Methanogens range has already been studied and species were isolated from a extensive scale of environments: gut of terrestrial arthropods (Hackstein and Stumm, 1994), termite guts (Ohkuma et al, 1999), hydrothermal vents (Takai and Horikoshi, 1999), hydrocarboncontaminated soils (Watanabe et al, 2002), ocean (Reeburgh, 2007) sediment soils (Bridgham et al, 2013), freshwater (Borrel et al, 2011) and humans (Saengkerdsub and Ricke, 2014). Among submerged soils, rice field soils have been widely examined (Ramakrishnan et al, 2001).…”