Abstract
BackgroundBacteria involved in ruminal formation of trans-10 intermediates are unclear. Therefore, this study aimed at identifying rumen bacteria that produce trans-10 intermediates from 18-carbon unsaturated fatty acids.ResultsPure cultures of 28 rumen bacterial species were incubated individually in the presence of 40 μg/mL 18:3n-3, 18:2n-6 or trans-11 18:1 under control or lactate-enriched (200 mM Na lactate) conditions for 24 h. Of the 28 strains, Cutibacterium acnes (formerly Propionibacterium acnes) was the only bacterium found to produce trans-10 intermediates from 18:3n-3 and 18:2n-6, irrespective of the growth condition. To further assess the potential importance of this species in the trans-11 to trans-10 shift, different biomass ratios of Butyrivibrio fibrisolvens (as a trans-11 producer) and C. acnes were incubated in different growth media (control, low pH and 22:6n-3 enriched media) containing 40 μg/mL 18:2n-6. Under control conditions, a trans-10 shift, defined in the current study as trans-10/trans-11 ≥ 0.9, occurred when the biomass of C. acnes represented between 90 and 98% of the inoculum. A low pH or addition of 22:6n-3 inhibited cis-9, trans-11 CLA and trans-10, cis-12 CLA formation by B. fibrisolvens and C. acnes, respectively, whereby C. acnes seemed to be more tolerant. This resulted in a decreased biomass of C. acnes required at inoculation to induce a trans-10 shift to 50% (low pH) and 90% (22:6n-3 addition).ConclusionsAmong the bacterial species studied,C. acnes was the only bacterium that have the metabolic ability to produce trans-10 intermediates from 18:3n-3 and 18:2n-6. Nevertheless, this experiment revealed that it is unlikely that C. acnes is the only or predominant species involved in the trans-11 to trans-10 shift in vivo.
Highlights
Bacteria involved in ruminal formation of trans-10 intermediates are unclear
This experiment revealed that it is unlikely that C. acnes is the only or predominant species involved in the trans-11 to trans-10 shift in vivo
Butyrivibrio fibrisolvens D1 showed an accumulation of trans-11 intermediates, when incubated with 18:3n-3 or 18:2n-6
Summary
Bacteria involved in ruminal formation of trans-10 intermediates are unclear. This study aimed at identifying rumen bacteria that produce trans-10 intermediates from 18-carbon unsaturated fatty acids. The formation in the rumen of various biohydrogenation intermediates seems the responsibility of several bacterial species There might be other bacteria producing trans-11 intermediates, some bacteria involved in the trans-11 biohydrogenation pathway have been identified. Butyrivibrio fibrisolvens was the first ruminal bacterial species found to carry out biohydrogenation of 18:2n-6 and 18:3n-3 in vitro through the trans-11 pathway [6]. Further research identified other Butyrivibrio spp., Pseudobutyrivibrio spp. and Sharpea spp. as capable of producing trans-11 intermediates All members of the (Pseudo) butyrivibrio group, including B. fibrisolvens and B. proteoclasticus, and Sharpea spp. convert 18:2n-6 much more rapidly than other species [10, 14]
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