Nitrogen metabolism in rumen bacteria can be characterised by their N isotopic signature
Résumé
The N use efficiency (NUE) of ruminants is negatively correlated to the natural 15N
enrichment of ruminants’ tissues over their diets (Δ15Nanimal-diet). The metabolism of rumen
bacteria, which strongly discriminates against 15N utilisation, may contribute to this link but
little is known about the role of individual bacteria. In this study, we characterised the Δ15N of
three metabolically different rumen bacteria, a cellulolytic ammonia-consuming, a hyperammonia
producing and a proteolytic organism, grown in pure culture with different N
sources and levels. The N isotopic signatures significantly changed across the 3 rumen
bacteria. Although we failed to observe a higher Δ15Nbacteria-substrate when proteolysis and
ammonia production was favoured, our results confirm a strong 15N depletion with the
ammonia-consuming bacterium. This may suggest that 15N depleted ammonia-consuming
bacteria improves the NUE in the rumen.
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