Toxicity of unsaturated fatty acids to the biohydrogenating ruminal bacterium, Butyrivibrio fibrisolvens.
BACKGROUND
Health-promoting polyunsaturated fatty acids (PUFA) are abundant in forages grazed by ruminants and in vegetable and fish oils used as dietary supplements, but only a small proportion of PUFA finds its way into meat and milk, because of biohydrogenation in the rumen. Butyrivibrio fibrisolvens plays a major role in this activity. The aim of this study was to investigate the mechanisms by which PUFA affect the growth of B. fibrisolvens, how PUFA are metabolized and the metabolic response to growth in the presence of PUFA.


RESULTS
Linoleic acid (LA; cis-9, cis-12-18:2) and alpha-linolenic acid (LNA; cis-9, cis-12, cis-15-18:3) increased the lag phase of B. fibrisolvens JW11, LNA having the greater effect. Growth was initiated only when the PUFA had been converted to vaccenic acid (VA; trans-11-18:1). The major fish oil fatty acids, eicosapentaenoic acid (EPA; 20:5(n-3)) and docosahexaenoic acid (DHA; 22:6(n-3)), were not metabolized and prevented growth. Cellular integrity, as determined fluorimetrically by propidium iodide (PI) ingression, was affected as much by 18:1 fatty acids, including VA, as 18:2 fatty acids. The methyl esters of LNA, LA, EPA and DHA had no effect on growth or other measurements. The ATP pool decreased by 2/3 when LA was added to growing bacteria, whereas most acyl CoA pools decreased by >96%.


CONCLUSIONS
It was concluded that biohydrogenation occurs to enable B. fibrisolvens to survive the bacteriostatic effects of PUFA, and that the toxicity of PUFA is probably mediated via a metabolic effect rather than disruption of membrane integrity.
Maia
Margarida R G
MR
Rowett Institute of Nutrition and Health, University of Aberdeen, Bucksburn, Aberdeen AB21 9SB, UK.
Chaudhary
Lal C
LC
Bestwick
Charles S
CS
Richardson
Anthony J
AJ
McKain
Nest
N
Larson
Tony R
TR
Graham
Ian A
IA
Wallace
Robert J
RJ
D000214:Acyl Coenzyme A / Q000032:analysis; D000255:Adenosine Triphosphate / Q000032:analysis; D000818:Animals; D045856:Butyrivibrio / Q000187:drug effects* / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects; D003470:Culture Media; D005231:Fatty Acids, Unsaturated / Q000378:metabolism / Q000494:pharmacology*; D005434:Flow Cytometry; D006865:Hydrogenation; D019787:Linoleic Acid / Q000378:metabolism / Q000494:pharmacology; D050356:Lipid Metabolism; D012756:Sheep / Q000382:microbiology; D019354:Sodium Lactate / Q000494:pharmacology
D000214:Acyl Coenzyme A; D003470:Culture Media; D005231:Fatty Acids, Unsaturated; D000255:Adenosine Triphosphate; D019787:Linoleic Acid; D019354:Sodium Lactate