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Lipgene

Rowett Research Institute

The Microbial Metabolism Group of the Rowett Research Institute (http://www.rowett.ac.uk/divisions/ Gut/microbial_meta/microbial_meta.html) plays a fundamental role in the Work Package on Animal Nutrition in Lipgene. The Group Leader is Dr R. John Wallace (John.Wallace@rowett.ac.uk), with Dr Delphine Paillard (D.Paillard@rowett.ac.uk) appointed as post-doctoral fellow to work on the project.

The aim of the Rowett contribution to Lipgene is to analyse retrospectively, using real-time PCR based on 16S rRNA genes, the microbial population of digesta samples generated in the animal experiments done in Reading and at MTT in Finland. This analysis should reveal changes in the ruminal flora and fauna which cause different fatty acid composition of milk from cows on different dietary regimens.

The Microbial Metabolism group has studied rumen microbial fermentation for many years, focusing lately on biohydrogenation of fatty acids in the rumen. The group of bacteria loosely called Butyrivibrio fibrisolvens is responsible for biohydrogenation, whereby unsaturated C-18 fatty acids are converted via conjugated linoleic acid and trans-vaccenic acid to stearic acid (Fig. 1).

The different branches of the phylogenetic tree carry out different functions: the bacteria in one branch convert linoleic acid as far as trans-vaccenic acid; bacteria in the other branch are much more sensitive to the toxic effects of unsaturated fatty acids and complete the biohydrogenation to stearic acid (Fig. 2).

One of these isolates is the 'Fusocillus' which was identified many years ago to be a stearic acid producer but never characterised by molecular genetic means. Real-time PCR will be developed, based on 16S rRNA genes, to quantify how the population sizes of these two branches correlate with milk composition, using digesta samples generated by the other partners in the Animal Nutrition work package. Once the relation between microbial population and milk composition has been described, it should be possible to target specific sub-populations of Butyrivibrio fibrisolvens in order to modify milk composition in specific ways.

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Fig. 1) Conversion of linoleic acid to stearic acid in the rumen: biohydrogenation
(Fig. 1 above)
Conversion of linoleic acid to stearic acid in the rumen: biohydrogenation.
(View higher resolution version (opens a new window) "rowetta-1_v2.jpg", 236KB)


(Fig. 2) Phylogenetic tree of Butyrivibrio fibrisolvens and related isolates, and products formed from linoleic acid

(Fig. 2 above)
Phylogenetic tree of Butyrivibrio fibrisolvens and related isolates, and products formed from linoleic acid
. (View higher resolution version (opens a new window), "rowetta-2_v2.jpg", 628KB)

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