Toxicity of unsaturated fatty acids to the biohydrogenating ruminal bacterium, <it>Butyrivibrio fibrisolvens</it>

• Main Authors: Bestwick Charles S, Chaudhary Lal C, Maia Margarida RG, Richardson Anthony J, McKain Nest, Larson Tony R, Graham Ian A, Wallace Robert J
• Format: Article
• Language: English
• Published: BMC 2010-02-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/10/52

<p/> <p>Background</p> <p>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. <it>Butyrivibrio fibrisolvens </it>plays a major role in this activity. The aim of this study was to investigate the mechanisms by which PUFA affect the growth of <it>B. fibrisolvens</it>, how PUFA are metabolized and the metabolic response to growth in the presence of PUFA.</p> <p>Results</p> <p>Linoleic acid (LA; <it>cis</it>-9, <it>cis</it>-12-18:2) and α-linolenic acid (LNA; <it>cis</it>-9, <it>cis</it>-12, <it>cis</it>-15-18:3) increased the lag phase of <it>B. fibrisolvens </it>JW11, LNA having the greater effect. Growth was initiated only when the PUFA had been converted to vaccenic acid (VA; <it>trans-</it>11-18:1). The major fish oil fatty acids, eicosapentaenoic acid (EPA; 20:5(<it>n-</it>3)) and docosahexaenoic acid (DHA; 22:6(<it>n-</it>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%.</p> <p>Conclusions</p> <p>It was concluded that biohydrogenation occurs to enable <it>B. fibrisolvens </it>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.</p>