Chemical markers for rumen methanogens and methanogenesis
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TLDR
It is speculated that variation in the distribution and kinetics of methanogens in the rumen may affect the survival and functioning of Archaea in theRumen and therefore contribute to genetic variation in methane production.Abstract:
The targeting of mcrA or 16S rRNA genes by quantitative PCR (qPCR) has become the dominant method for quantifying methanogens in rumen. There are considerable discrepancies between estimates based on different primer sets, and the literature is equivocal about the relationship with methane production. There are a number of problems with qPCR, including low primer specificity, multiple copies of genes and multiple genomes per cell. Accordingly, we have investigated alternative markers for methanogens, on the basis of the distinctive ether lipids of archaeal cell membranes. The membranes of Archaea contain dialkyl glycerol ethers such as 2,3-diphytanayl-O-sn-glycerol (archaeol), and glycerol dialkyl glycerol tetraethers (GDGTs) such as caldarchaeol (GDGT-0) in different proportions. The relationships between estimates of methanogen abundance using qPCR and archaeol measurements varied across primers. Studies in other ecosystems have identified environmental effects on the profile of ether lipids in Archaea. There is a long history of analysing easily accessible samples, such as faeces, urine and milk, to provide information about digestion and metabolism in livestock without the need for intrusive procedures. Purine derivatives in urine and odd-chain fatty acids in milk have been used to study rumen function. The association between volatile fatty acid proportions and methane production is probably the basis for empirical relationships between milk fatty acid profiles and methane production. However, these studies have not yet identified consistent predictors. We have evaluated the relationship between faecal archaeol concentration and methane production across a range of diets in studies on beef and dairy cattle. Faecal archaeol is diagnostic for ruminant faeces being below the limit of detection in faeces from non-ruminant herbivores. The relationship between faecal archaeol and methane production was significant when comparing treatment means across diets, but appears to be subject to considerable between-animal variation. This variation was also evident in the weak relationship between archaeol concentrations in rumen digesta and faeces. We speculate that variation in the distribution and kinetics of methanogens in the rumen may affect the survival and functioning of Archaea in the rumen and therefore contribute to genetic variation in methane production. Indeed, variation in the relationship between the numbers of micro-organisms present in the rumen and those leaving the rumen may explain variation in relationships between methane production and both milk fatty acid profiles and faecal archaeol. As a result, microbial markers in the faeces and milk are unlikely to relate well back to methanogenesis in the rumen. This work has also highlighted the need to describe methanogen abundance in all rumen fractions and this may explain the difficulty interpreting results on the basis of samples taken using stomach tubes or rumenocentesis.read more
Citations
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Oral Samples as Non-Invasive Proxies for Assessing the Composition of the Rumen Microbial Community.
Ilma Tapio,Kevin J. Shingfield,Nest McKain,Aurélie Bonin,Daniel Fischer,Ali R. Bayat,Johanna Vilkki,Pierre Taberlet,Timothy J. Snelling,R. John Wallace +9 more
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References
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Distributional variations in marine crenarchaeotal membrane lipids: a new tool for reconstructing ancient sea water temperatures?
TL;DR: In this article, a significant linear correlation was found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaota and the annual mean sea surface temperatures, suggesting that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives.
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Biochemistry of methanogenesis: a tribute to Marjory Stephenson:1998 Marjory Stephenson Prize Lecture
TL;DR: In 1933, Stephenson & Stickland published that they had isolated from river mud, by the single cell technique, a methanogenic organism capable of growth in an inorganic medium with formate as the sole carbon source.
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A novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids
Ellen C. Hopmans,Johan W.H. Weijers,Enno Schefuß,Lydie Herfort,Jaap S. Sinninghe Damsté,Stefan Schouten +5 more
TL;DR: In this paper, a tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high-performance liquid chromatography/mass spectrometry (HPLC/MS) was proposed.
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The organic geochemistry of glycerol dialkyl glycerol tetraether lipids: A review
TL;DR: Progress made over the last decade in the analysis, occurrence and recognition of sources of GDGTs, their applications as biomarker lipids, and the development and application of proxies based on their distributions are reviewed.
Journal ArticleDOI
Environmental controls on bacterial tetraether membrane lipid distribution in soils
Johan W.H. Weijers,Stefan Schouten,Jurgen C. van den Donker,Ellen C. Hopmans,Jaap S. Sinninghe Damsté +4 more
TL;DR: In this paper, the relative distribution of soil-derived GDGT membrane lipids can be used in palaeoenvironmental studies to estimate past annual mean air temperature and soil pH.