title: Methanogen colonisation does not significantly alter acetogen diversity in lambs isolated 17 h after birth and raised aseptically.
abstract: Reductive acetogenesis is not competitive with methanogenesis in adult ruminants, whereas acetogenic bacteria are the dominant hydrogenotrophs in the early rumen microbiota. The ecology of hydrogenotrophs in the developing rumen was investigated using young lambs, raised in sterile isolators, and conventional adult sheep. Two lambs were born naturally, left with their dams for 17 h and then placed into a sterile isolator and reared aseptically. They were inoculated with cellulolytic bacteria and later with Methanobrevibacter sp. 87.7 to investigate the effect of methanogen establishment on the rumen acetogen population since they lacked cultivable representatives of methanogens. Putative acetogens were investigated by acetyl-CoA synthase and formyltetrahydrofolate synthetase gene analysis and methanogens by methyl coenzyme reductase A gene analysis. Unexpectedly, a low abundant but diverse population of methanogens (predominantly Methanobrevibacter spp.) was identified in isolated lambs pre-inoculation with Mbb. sp 87.7, which was similar to the community structure in conventional sheep. In contrast, potential acetogen diversity in isolated lambs and conventional sheep was different. Potential acetogens affiliated between the Lachnospiraceae and Clostridiaceae in conventional sheep  and with the Blautia genus and the Lachnospiraceae in isolated lambs. The establishment of Mbb. sp. 87.7 (1,000-fold increase in methanogens) did not substantially affect acetogen diversity.
authors.affiliation: CSIRO Livestock Industries, St. Lucia, QLD 4067, Australia. emma.gagen@gmail.com
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Gagen
authors.forename: Pascale
authors.initials: P
authors.lastname: Mosoni
authors.forename: Stuart E
authors.initials: SE
authors.lastname: Denman
authors.forename: Rafat
authors.initials: R
authors.lastname: Al Jassim
authors.forename: Christopher S
authors.initials: CS
authors.lastname: McSweeney
authors.forename: Evelyne
authors.initials: E
authors.lastname: Forano
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000382:microbiology; D001207:Asepsis; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D017753:Ecosystem; D008697:Methane / Q000378:metabolism*; D041581:Methanobrevibacter / Q000254:growth & development; D008969:Molecular Sequence Data; D012417:Rumen / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D034561:Sheep, Domestic / Q000254:growth & development* / Q000382:microbiology; D013997:Time Factors
chemical_list: D002482:Cellulose; D008697:Methane; D019342:Acetic Acid