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Applied and Environmental Microbiology, October 2007, p. 6391-6403, Vol. 73, No. 20
0099-2240/07/$08.00+0     doi:10.1128/AEM.00181-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Establishment and Development of Ruminal Hydrogenotrophs in Methanogen-Free Lambs{triangledown}

Gérard Fonty,1* Keith Joblin,2 Michel Chavarot,1 Remy Roux,1 Graham Naylor,2 and Fabien Michallon1

Unité de Microbiologie, INRA, Centre de Clermont-Ferrand-Theix, 63177 Aubière Cedex, France,1 Grasslands Research Centre, AgResearch, Private Bag 11008, Palmerston North 4442, New Zealand2

Received 24 January 2007/ Accepted 24 July 2007

The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid concentrations for lambs lacking ruminal methanogens were lower but not markedly dissimilar from those for conventional lambs reared on the same diet. A high population density (107 to 108 cells g–1) of ruminal acetogens slowly developed in methanogen-free lambs. Sulfate- and fumarate-reducing bacteria were present, but their population densities were highly variable. In methanogen-free lambs, the hydrogen capture from fermentation was low (28 to 46%) in comparison with that in lambs containing ruminal methanogens (>90%). Reductive acetogenesis was not a significant part of ruminal fermentation in conventional lambs but contributed 21 to 25% to the fermentation in methanogen-free meroxenic animals. Ruminal H2 utilization was lower in lambs lacking ruminal methanogens, but when a methanogen-free lamb was inoculated with a methanogen, the ruminal H2 utilization was similar to that in conventional lambs. H2 utilization in lambs containing a normal ruminal microflora was age dependent and increased with the animal age. The animal age effect was less marked in lambs lacking ruminal methanogens. Addition of fumarate to rumen contents from methanogen-free lambs increased H2 utilization. These findings provide the first evidence from animal studies that reductive acetogens can sustain a functional rumen and replace methanogens as a sink for H2 in the rumen.

* Corresponding author. Present address: Laboratoire de Biologie des Protistes, UMR CNRS 6023, Université Blaise Pascal, 63177 Aubière cedex, France. Phone: 33 (0)4 73 40 74 60. Fax: 33 (0)4 73 40 76 70. E-mail: gerard.FONTY{at}univ-bpclermont.fr

{triangledown} Published ahead of print on 3 August 2007.

Applied and Environmental Microbiology, October 2007, p. 6391-6403, Vol. 73, No. 20
0099-2240/07/$08.00+0     doi:10.1128/AEM.00181-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Karnati, S. K. R., Yu, Z., Firkins, J. L. (2009). Investigating unsaturated fat, monensin, or bromoethanesulfonate in continuous cultures retaining ruminal protozoa. II. Interaction of treatment and presence of protozoa on prokaryotic communities. J DAIRY SCI 92: 3861-3873 [Abstract] [Full Text]  


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