Methanogen genomics to discover targets for methane mitigation technologies and options for alternative H2 utilisation in the rumen

Attwood, Graeme T.; McSweeney, Christopher S.

doi:10.1071/ea07203

Cited by 59 publications

(48 citation statements)

References 57 publications

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Section: Mitigation Through Biotechnologiesmentioning

confidence: 99%

“…The recent completion of the complete genome sequence of Methanobrevibacter ruminantium by New Zealand scientists (http://www.pggrc.co.nz) opens the way for the identification of specific immunological targets that could be common to other methanogens found in the rumen. This information could be used for the development of second-generation vaccines (Attwood and McSweeney, 2008).Passive immunisation was also recently assayed using antibodies, which were produced in laying hens, against three common methanogens present in the digestive tract of animals. Treatments using whole eggs decreased transiently CH 4 production in vitro but the effect was lost at the end of the 24-h incubation (Cook et al, 2008).…”

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confidence: 99%

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Methane mitigation in ruminants: from microbe to the farm scale

Martin

Morgavi

Doreau

2010

Animal

747

657

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Decreasing enteric methane (CH 4 ) emissions from ruminants without altering animal production is desirable both as a strategy to reduce global greenhouse gas (GHG) emissions and as a means of improving feed conversion efficiency. The aim of this paper is to provide an update on a selection of proved and potential strategies to mitigate enteric CH 4 production by ruminants. Various biotechnologies are currently being explored with mixed results. Approaches to control methanogens through vaccination or the use of bacteriocins highlight the difficulty to modulate the rumen microbial ecosystem durably. The use of probiotics, i.e. acetogens and live yeasts, remains a potentially interesting approach, but results have been either unsatisfactory, not conclusive, or have yet to be confirmed in vivo. Elimination of the rumen protozoa to mitigate methanogenesis is promising, but this option should be carefully evaluated in terms of livestock performances. In addition, on-farm defaunation techniques are not available up to now. Several feed additives such as ionophores, organic acids and plant extracts have also been assayed. The potential use of plant extracts to reduce CH 4 is receiving a renewed interest as they are seen as a natural alternative to chemical additives and are well perceived by consumers. The response to tannin-and saponincontaining plant extracts is highly variable and more research is needed to assess the effectiveness and eventual presence of undesirable residues in animal products. Nutritional strategies to mitigate CH 4 emissions from ruminants are, without doubt, the most developed and ready to be applied in the field. Approaches presented in this paper involve interventions on the nature and amount of energy-based concentrates and forages, which constitute the main component of diets as well as the use of lipid supplements. The possible selection of animals based on low CH 4 production and more likely on their high efficiency of digestive processes is also addressed. Whatever the approach proposed, however, before practical solutions are applied in the field, the sustainability of CH 4 suppressing strategies is an important issue that has to be considered. The evaluation of different strategies, in terms of total GHG emissions for a given production system, is discussed.Keywords: methane, greenhouse gases, ruminant, mitigation strategies Implications Methane (CH 4 ) mitigation in ruminants is possible through various strategies. Today, the feeding management approach is the most developed. Other strategies (biotechnologies, additives) are promising but the diversity and plasticity of functions of the rumen bacterial and methanogenic communities may be a limiting factor for their successful application. A possible selection of animals on CH 4 production and more likely on digestive processes is evocated. In any case, before practical solutions are proposed for field application more research in vivo is needed. The sustainability of CH 4 -suppressing strategies is also an important issue and they mi...

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Section: Mitigation Through Biotechnologiesmentioning

confidence: 99%

mentioning

confidence: 99%

Methane mitigation in ruminants: from microbe to the farm scale

Martin

Morgavi

Doreau

2010

Animal

747

657

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“…Understanding hydrogenotrophy in these gut systems may provide insight into mechanisms for redirecting hydrogen away from methanogenesis in ruminants. Acetogenesis may represent a significant hydrogen sink in the foregut of native Australian marsupials (2), and these animals may be a source of novel acetogens.…”

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confidence: 99%

Functional Gene Analysis Suggests Different Acetogen Populations in the Bovine Rumen and Tammar Wallaby Forestomach

Gagen

Denman

Padmanabha

et al. 2010

Appl Environ Microbiol

113

111

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Reductive acetogenesis via the acetyl coenzyme A (acetyl-CoA) pathway is an alternative hydrogen sink to methanogenesis in the rumen. Functional gene-based analysis is the ideal approach for investigating organisms capable of this metabolism (acetogens). However, existing tools targeting the formyltetrahydrofolate synthetase gene (fhs) are compromised by lack of specificity due to the involvement of formyltetrahydrofolate synthetase (FTHFS) in other pathways. Acetyl-CoA synthase (ACS) is unique to the acetyl-CoA pathway and, in the present study, acetyl-CoA synthase genes (acsB) were recovered from a range of acetogens to facilitate the design of acsB-specific PCR primers. fhs and acsB libraries were used to examine acetogen diversity in the bovine rumen and forestomach of the tammar wallaby (Macropus eugenii), a native Australian marsupial demonstrating foregut fermentation analogous to rumen fermentation but resulting in lower methane emissions. Novel, deduced amino acid sequences of acsB and fhs affiliated with the Lachnospiraceae in both ecosystems and the Ruminococcaeae/Blautia group in the rumen. FTHFS sequences that probably originated from nonacetogens were identified by low "homoacetogen similarity" scores based on analysis of FTHFS residues, and comprised a large proportion of FTHFS sequences from the tammar wallaby forestomach. A diversity of FTHFS and ACS sequences in both ecosystems clustered between the Lachnospiraceae and Clostridiaceae acetogens but without close sequences from cultured isolates. These sequences probably originated from novel acetogens. The community structures of the acsB and fhs libraries from the rumen and the tammar wallaby forestomach were different (LIBSHUFF, P < 0.001), and these differences may have significance for overall hydrogenotrophy in both ecosystems.Methane is a potent greenhouse gas that is implicated in global warming (35). Of the 600 Tg of methane released into the atmosphere each year, 55 to 70% is anthropogenic (48). Enteric fermentation of ruminant livestock is the largest source of anthropogenic methane, contributing between 20 and 25% (48). During enteric fermentation, archaea in the rumen (methanogens) produce methane mainly through the stepwise reduction of CO 2 (4H 2 ϩ CO 2 3 CH 4 ϩ 2H 2 O) (47). As well as contributing to greenhouse gas emissions, methanogenesis is energetically wasteful representing a loss of between 2 and 12% ingested feed energy (23). Reductive acetogenesis is a hydrogenotrophic pathway (4H 2 ϩ 2CO 2 3 CH 3 COOH ϩ 2H 2 O) that results in an energy gain for ruminant livestock through the production of acetate (22) and could be an alternative hydrogen sink to methanogenesis if methanogenesis is suppressed (16).The bacteria capable of reductive acetogenesis via the acetyl coenzyme A (acetyl-CoA) pathway (acetogens) exist in a range of environments, including sediments, wastewater treatment systems, soils, and animal gut systems, and they are likely to be natural microbiota of all ruminants (11,22). Naturally, however, reductive acetog...

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“…The last step is catalysed with Methyl-Coenzyme M reductase of reduction of CO2 to CH4 by hydrogenotropic methanogenic archaea [77]. Details of the enteric methane production are described in many papers e.g., [78]; [79]; [80]; [81]; [82] and prediction equations are given, e.g., [6]; [83]; [84]; [85]; [86]; [87,88]; [89].…”

Section: Methane (Ch4)mentioning

confidence: 99%

“…Methyl-Coenzyme M reductase catalyses the last step of reduction of CO2 to CH4 by hydrogenotrophic methanogenic archaea [77].…”

Section: Rumen Fermentation and Methane (Ch4) Emissionmentioning

confidence: 99%