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Journal of Bacteriology, March 2007, p. 2566-2570, Vol. 189, No. 6
0021-9193/07/$08.00+0 doi:10.1128/JB.01359-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
Metabolism of Linoleic Acid by Human Gut Bacteria: Different Routes for Biosynthesis of Conjugated Linoleic Acid
Estelle Devillard,
Freda M. McIntosh,
Sylvia H. Duncan, and
R. John Wallace*
Gut Health Division, Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen, AB21 9SB, United Kingdom
Received 28 August 2006/
Accepted 26 December 2006

ABSTRACT
A survey of 30 representative strains of human gram-positive
intestinal bacteria indicated that
Roseburia species were among
the most active in metabolizing linoleic acid (
cis-9,
cis-12-18:2).
Different
Roseburia spp. formed either vaccenic acid (
trans-11-18:1)
or a 10-hydroxy-18:1; these compounds are precursors of the
health-promoting conjugated linoleic acid
cis-9,
trans-11-18:2
in human tissues and the intestine, respectively.

TEXT
Linoleic acid (LA) (
cis-9,
cis-12-18:2) is metabolized in the
human colon via conjugated linoleic acids (CLA) (mainly
cis-9,
trans-11-18:2)
to vaccenic acid (VA) (
trans-11-18:1) (both of the latter compounds
are considered to be beneficial for health [
5,
11,
27,
28,
31,
41]) and then to stearic acid (18:0) (
17,
26). A similar pathway
occurs in the rumen (
12,
20), where this process, commonly known
as biohydrogenation, has important implications for the fatty
acid composition of meat and milk (
22,
38). The microbiology
of biohydrogenation in the rumen has received a great deal of
attention (
12,
32,
40,
42), but similar investigations have
not been carried out for the human intestinal microbiota. Therefore,
the aims of the present study were to identify human gut bacteria
that can perform fatty acid biohydrogenation and to assess their
likely importance in the mixed intestinal ecosystem. We found
that
Roseburia spp. were probably the most important organisms;
some
Roseburia species metabolized LA by the same pathway found
in ruminal bacteria (
20,
32), while others formed a hydration
product that is a precursor of CLA in the mixed community.
Thirty bacterial strains (2 lactobacilli, 1 lactococcus, 5 propionibacteria, 3 bifidobacteria, and 19 strains of the low-G+C-content Clostridium cluster) isolated from or related to bacteria found in the human large intestine were studied to determine their ability to metabolize LA (Table 1). The bacteria were grown either in the liquid form of anaerobic basal M2 medium (13) or in the same medium supplemented with 50 µg/ml LA. For labeling experiments the medium was prepared using enough deuterium oxide to provide around 50% enrichment of the medium water. The linoleate isomerase activity in bacteria grown on unsupplemented M2 medium was determined by the method described by W
sowska et al. (43). The methods used for extraction and derivatization of the total fatty acids to fatty acid methyl esters (FAME) and the identification methods were similar to the methods described by Devillard et al. (7). In order to determine the fate of the hydroxy-18:1 fatty acid (HFA) produced by some of the Roseburia isolates, Roseburia intestinalis L1-952 was grown in M2 medium containing 50 µg/ml LA, the culture was centrifuged (10,000 x g, 10 min, 4°C), and the supernatant was used to prepare a modified M2 medium enriched in HFA. This medium was inoculated with freshly voided human feces from two omnivorous volunteers consuming a Western diet, which had been diluted (0.2 g in 1 ml) in sterile anaerobic 0.1 M potassium phosphate buffer (pH 7.0). Duplicate aliquots of each fecal sample were removed after different times for fatty acid determination for up to 72 h.
The linoleate isomerase activity was >10 nmol CLA formed
(mg protein)
1 min
1 in 8 of the 30 isolates (Table
1), and
Butyrivibrio fibrisolvens 16.4 and two strains of
Roseburia inulinivorans (A2-194 and L1-83) exhibited the highest activity.
When inoculated into medium containing LA, most of the 30 strains
showed a lag time before they started to grow (Table
1). The
same eight isolates that had high levels of isomerase activity
also metabolized LA most extensively (Table
1). The final products
for these strains were VA for the
Roseburia and
B. fibrisolvens isolates, a mixture of CLA (mainly
cis-9,
trans-11-18:2,
trans-9,
trans-11-18:2,
and
trans-10,
cis-12-18:2) for
Propionibacterium freudenreichii subsp.
shermani, and
cis-9,
trans-11-18:2 and
trans-9,
trans-11-18:2
for
Bifidobacterium breve (Table
1). Thus, it appears that whereas
other species produced a mixture of CLA products, bacteria belonging
to
Clostridium cluster XIVa formed one product, either VA or
HFA. Thirteen strains, belonging to both phylogenetic groups,
metabolized LA (range, 26% to 88%) despite their low linoleate
isomerase activity (Table
1). Gas chromatography traces indicated
that all these strains produced the same compound, which was
subsequently identified by gas chromatography-mass spectrometry
(Fig.
1A). The main fragmentation in mass spectrometry led to
the formation of ions at
m/z 169 and 201, which are characteristic
of a 10-HFA with the first 10 bonds saturated. When
R. intestinalis L1-952 was grown in the presence of 50 µg/ml LA and deuterium
oxide, the two major peaks were shifted to ions at
m/z 171 and
203 (Fig.
1B). This shift corresponded to an addition of deuterium
atoms at the double bond between carbons 9 and 10, suggesting
that hydration occurred on this double bond (Fig.
1B). The location
of the double bond could not be determined by analysis of the
FAME. However, the signature masses at
m/z 201 and 294 identified
in 10-hydroxy-
cis-12-18:1 by Schroepfer et al. (
37) were present
in the FAME spectrum. This information, together with purely
biochemical considerations and comparison of the elution time
of the FAME with that of ricinoleic acid (12-hydroxy-
cis-9-18:1),
indicated that the product was most likely 10-hydroxy-
cis-12-18:1.
Modified M2 medium prepared from the culture supernatant of
R. intestinalis L1-952 initially contained 5 µg/ml LA
and 25 µg/ml HFA. The main fatty acids produced during
incubation with diluted feces were
cis-9,
trans-11-18:2, VA,
and stearic acid (Fig.
2). After a few hours, LA was almost
completely metabolized, but the synthesis of CLA, VA, and stearic
acid continued and corresponded to the disappearance of HFA
(Fig.
2). Thus, we concluded that HFA is a precursor of
cis-9,
trans-11-18:2
in the mixed community. None of the pure cultures examined metabolized
the HFA further.
Animal studies and clinical trials have indicated that CLA may
be useful in improving human health (
5,
27,
31). The uptake
of CLA formed in the intestine seems to be minor (
17). However,
local effects on gut tissue might be anticipated. It is now
well established that CLA have antiproliferative and anti-inflammatory
effects on colonocytes (
4,
19), so provision of CLA in the intestinal
lumen could be considered beneficial, particularly for inflammatory
bowel diseases, such as ulcerative colitis and Crohn's disease
(
10). Bacteria from other ecosystems and from food products
which are also found in the human gut, including strains of
Lactobacillus,
Propionibacterium, and
Bifidobacterium (
1,
6,
15,
23,
33,
34), have been known for some time to possess the
ability to generate CLA. For the first time, we found here that
the more abundant bacterial species belonging to clostridial
clusters IV and XIVa also metabolize LA at some of the highest
rates of all bacteria investigated, forming products that can
be precursors of CLA (Fig.
3). Given the greater abundance of
Clostridium-like bacteria in the human intestinal microbiota
(
9)the numbers of lactobacilli, propionibacteria, and
bifidobacteria are low, less than 5% of the total microbiota
(
2,
21)it may be deduced that LA metabolism by this major
group is quantitatively more important than LA metabolism by
the
Lactobacillus,
Propionibacterium, and
Bifidobacterium groups.
The discovery that HFA is a precursor of
cis-9,
trans-11-18:2
in the mixed intestinal community is also new, leading to the
likely scheme of CLA formation shown in Fig.
3. Similar importance
of HFA was proposed for a
Lactobacillus sp., involving a hydration/dehydration
process (
30). No similar role for HFA has been postulated for
bacteria in the rumen, where biohydrogenation is a quantitatively
very important activity (
12,
32).
The final product of LA metabolism by mixed fecal microbiota was shown here to be stearic acid, as shown previously by Howard and Henderson (14), yet none of the strains tested here produced stearate from LA (Fig. 3). Searching for stearate producers in the rumen has been difficult, largely because these organisms are extraordinarily sensitive to the toxic effects of unsaturated fatty acids (25, 42). The same may be true of human intestinal bacteria. Thus, stearate producers and the species that convert HFA to CLA, both potentially very important reactions in the mixed ecosystem of the human intestine, remain to be identified.

ACKNOWLEDGMENTS
The Rowett Research Institute receives funding from the Scottish
Executive Environmental and Rural Affairs Department.
We thank David Brown, Graham Calder, and Maureen Annand for technical help and expertise. We thank Kevin Shingfield and William Christie for advice on fatty acid analysis. We are grateful to Harry Flint for helpful criticism of the manuscript.

FOOTNOTES
* Corresponding author. Mailing address: Rowett Research Institute, Bucksburn, Aberdeen, AB21 9SB, United Kingdom. Phone: 44(0)1224-716656. Fax: 44(0)1224-716687. E-mail:
john.wallace{at}rowett.ac.uk.

Published ahead of print on 5 January 2007. 

REFERENCES
1 - Alonso, L., E. P. Cuesta, and S. E. Gilliland. 2003. Production of free conjugated linoleic acid by Lactobacillus acidophilus and Lactobacillus casei of human intestinal origin. J. Dairy Sci. 86:1941-1946.[Abstract/Free Full Text]
2 - Aminov, R. I., A. W. Walker, S. H. Duncan, H. J. M. Harmsen, G. W. Welling, and H. J. Flint. 2006. Molecular diversity, cultivation, and improved fluorescent in situ hybridization detection of a dominant group of human gut bacteria related to Roseburia and Eubacterium rectale. Appl. Environ. Microbiol. 72:6371-6376.[Abstract/Free Full Text]
3 - Barcenilla, A., S. E. Pryde, J. C. Martin, S. H. Duncan, C. S. Stewart, C. Henderson, and H. J. Flint. 2000. Phylogenetic relationships of butyrate-producing bacteria from the human gut. Appl. Environ. Microbiol. 66:1654-1661.[Abstract/Free Full Text]
4 - Bassaganya-Riera, J., K. Reynolds, S. Martino-Catt, Y. Cui, L. Hennighausen, F. Gonzalez, J. Rohrer, A. U. Benninghoff, and R. Hontecillas. 2004. Activation of PPAR gamma and delta by conjugated linoleic acid mediates protection from experimental inflammatory bowel disease. Gastroenterology 127:777-791.[CrossRef][Medline]
5 - Belury, M. A. 2002. Dietary conjugated linoleic acid in health: physiological effects and mechanisms of action. Annu. Rev. Nutr. 22:505-531.[CrossRef][Medline]
6 - Coakley, M., R. P. Ross, M. Nordgren, G. Fitzgerald, R. Devery, and C. Stanton. 2003. Conjugated linoleic acid biosynthesis by human-derived Bifidobacterium species. J. Appl. Microbiol. 94:138-145.[CrossRef][Medline]
7 - Devillard, E., F. M. McIntosh, C. J. Newbold, and R. J. Wallace. 2006. Rumen ciliate protozoa contain high concentrations of conjugated linoleic acids and vaccenic acid, yet do not hydrogenate linoleic acid or desaturate stearic acid. Br. J. Nutr. 96:697-704.[Medline]
8 - Duncan, S. H., R. I. Aminov, K. P. Scott, P. Louis, T. B. Stanton, and H. J. Flint. 2006. Proposal of Roseburia faecis sp. nov., Roseburia hominis sp. nov., and Roseburia inulinivorans sp. nov., based on isolates from human feces. Int. J. Syst. Evol. Microbiol. 56:2437-2441.[Abstract/Free Full Text]
9 - Eckburg, P. B., E. M. Bik, C. N. Bernstein, E. Purdom, L. Dethlefsen, M. Sargent, S. R. Gill, K. E. Nelson, and D. A. Relman. 2005. Diversity of the human intestinal microbial flora. Science 308:1635-1638.[Abstract/Free Full Text]
10 - Greicius, G., V. Arulampalam, and S. Pettersson. 2004. A CLA's act: feeding away inflammation. Gastroenterology 127:994-996.[CrossRef][Medline]
11 - Ha, Y. L., N. K. Grimm, and M. W. Pariza. 1987. Anticarcinogens from fried ground beef: heat-altered derivatives of linoleic acid. Carcinogenesis 8:1881-1887.[Abstract/Free Full Text]
12 - Harfoot, C. G., and G. P. Hazlewood. 1997. Lipid metabolism in the rumen, p. 348-426. In P. N. Hobson and C. S. Stewart (ed.), The rumen microbial ecosystem. Chapman & Hall, London, United Kingdom.
13 - Hobson, P. N. 1969. Rumen bacteria. Methods Microbiol. 3B:133-149.
14 - Howard, F. A. C., and C. Henderson. 1999. Hydrogenation of polyunsaturated fatty acids by human colonic bacteria. Lett. Appl. Microbiol. 29:193-196.[CrossRef][Medline]
15 - Jiang, J., L. Bjorck, and R. Fonden. 1998. Production of conjugated linoleic acid by dairy starter cultures. J. Appl. Microbiol. 85:95-102.[CrossRef][Medline]
16 - Johnson, J. L., and C. S. Cummins. 1972. Cell wall composition and deoxyribonucleic acid similarities among the anaerobic coryneforms, classical propionibacteria, and strains of Arachnia propionica. J. Bacteriol. 109:1047-1066.[Abstract/Free Full Text]
17 - Kamlage, B., L. Hartmann, B. Gruhl, and M. Blaut. 1999. Intestinal microorganisms do not supply associated gnotobiotic rats with conjugated linoleic acid. J. Nutr. 129:2212-2217.[Abstract/Free Full Text]
18 - Kandler, O., K. O. Stetter, and R. Köhl. 1980. Lactobacillus reuteri sp. nov., a new species of heterofermentative lactobacilli. Zentbl. Bakteriol. Hyg. Abt. I Orig. Reihe C 1:264-269.
19 - Kemp, M. Q., B. D. Jeffy, and D. F. Romagnolo. 2003. Conjugated linoleic acid inhibits cell proliferation through a p53-dependent mechanism: effects on the expression of G1-restriction points in breast and colon cancer cells. J. Nutr. 133:3670-3677.[Abstract/Free Full Text]
20 - Kepler, C. R., K. P. Hirons, J. J. McNeill, and S. B. Tove. 1966. Intermediates and products of the biohydrogenation of linoleic acid by Butyrivibrio fibrisolvens. J. Biol. Chem. 241:1350-1354.[Abstract/Free Full Text]
21 - Lay, C., M. Sutren, V. Rochet, K. Saunier, J. Dore, and L. Rigottier-Gois. 2005. Design and validation of 16S rRNA probes to enumerate members of the Clostridium leptum subgroup in human fecal microbiota. Environ. Microbiol. 7:933-946.[CrossRef][Medline]
22 - Lin, H., T. D. Boylston, M. J. Chang, L. O. Luedecke, and T. D. Shultz. 1995. Survey of the conjugated linoleic acid contents of dairy products. J. Dairy Sci. 78:2358-2365.[Abstract]
23 - Lin, T. Y., C. W. Lin, and C. H. Lee. 1999. Conjugated linoleic acid concentration as affected by lactic cultures and added linoleic acid. Food Chem. 67:1-5.[CrossRef]
24 - Louis, P., S. H. Duncan, S. I. McCrae, J. Millar, M. S. Jackson, and H. J. Flint. 2004. Restricted distribution of the butyrate kinase pathway among butyrate-producing bacteria from the human colon. J. Bacteriol. 186:2099-2106.[Abstract/Free Full Text]
25 - Maia, M. R. G., L. C. Chaudhary, L. Figueres, and R. J. Wallace. Metabolism of polyunsaturated fatty acids and their toxicity to the microflora of the rumen. Antonie Leeuwenhoek, in press.
26 - McIntosh, F. M., R. J. Wallace, and E. Devillard. 2006. Variations in intermediates and products of linoleic acid biohydrogenation by two different human mixed colonic flora. Reprod. Nutr. Dev. 46(Suppl. 1):S52.
27 - Mensink, R. P. 2005. Metabolic and health effects of isomeric fatty acids. Curr. Opin. Lipidol. 16:27-30.[Medline]
28 - Miller, A., E. McGrath, C. Stanton, and R. Devery. 2003. Vaccenic acid (t11-18:1) is converted to c9,t11-CLA in MCF-7 and SW480 cancer cells. Lipids 38:623-632.[CrossRef][Medline]
29 - Moore, W. E. C., J. L. Johnson, and L. V. Holdeman. 1976. Emendation of Bacteroidaceae and Butyrivibrio and descriptions of Desulfomonas gen. nov. and ten new species of the genera Desulfomonas, Butyrivibrio, Eubacterium, and Ruminococcus. Int. J. Syst. Bacteriol. 26:238-252.[Abstract/Free Full Text]
30 - Ogawa, J., K. Matsumura, S. Kishino, Y. Omura, and S. Shimizu. 2001. Conjugated linoleic acid accumulation via 10-hydroxy-12-octadecaenoic acid during microaerobic transformation of linoleic acid by Lactobacillus acidophilus. Appl. Environ. Microbiol. 67:1246-1252.[Abstract/Free Full Text]
31 - Pariza, M. W. 2004. Perspective on the safety and effectiveness of conjugated linoleic acid. Am. J. Clin. Nutr. 79:1132S-1136S.[Abstract/Free Full Text]
32 - Polan, C. E., J. J. McNeill, and S. B. Tove. 1964. Biohydrogenation of unsaturated fatty acids by rumen bacteria. J. Bacteriol. 88:1056-1064.[Abstract/Free Full Text]
33 - Rainio, A., M. Vahvaselka, T. Suomalainen, and S. Laakso. 2001. Reduction of linoleic acid inhibition in production of conjugated linoleic acid by Propionibacterium freudenreichii ssp. shermanii. Can. J. Microbiol. 47:735-740.[CrossRef][Medline]
34 - Rosberg-Cody, E., R. P. Ross, S. Hussey, C. A. Ryan, B. P. Murphy, G. F. Fitzgerald, R. Devery, and C. Stanton. 2004. Mining the microbiota of the neonatal gastrointestinal tract for conjugated linoleic acid-producing bifidobacteria. Appl. Environ. Microbiol. 70:4635-4641.[Abstract/Free Full Text]
35 - Schleifer, K. H., J. Kraus, C. Dvorak, R. Kilpper-Baelz, M. D. Collins, and W. Fischer. 1985. Transfer of Streptococcus lactis and related streptococci to the genus Lactococcus gen. nov. Syst. Appl. Microbiol. 6:183-195.
36 - Schleifer, K. H., R. Plapp, and O. Kandler. 1968. Glycine as crosslinking bridge in the LL-diaminopimelic acid containing murein of Propionibacterium peterssonii. FEBS Lett. 1:287-290.[CrossRef][Medline]
37 - Schroepfer, G. J., Jr., W. G. Niehaus, Jr., and J. A. McCloskey. 1970. Enzymatic conversion of linoleic acid to 10D-hydroxy-
12-cis-octadecenoic acid. J. Biol. Chem. 245:3798-3801.[Abstract/Free Full Text] 38 - Scollan, N. D., N. J. Choi, E. Kurt, A. V. Fisher, M. Enser, and J. D. Wood. 2001. Manipulating the fatty acid composition of muscle and adipose tissue in beef cattle. Br. J. Nutr. 85:115-124.[Medline]
39 - Sharpe, M. E. 1955. A serological classification of lactobacilli. J. Gen. Microbiol. 12:107-122.[Abstract/Free Full Text]
40 - van de Vossenberg, J. L., and K. N. Joblin. 2003. Biohydrogenation of C18 unsaturated fatty acids to stearic acid by a strain of Butyrivibrio hungatei from the bovine rumen. Lett. Appl. Microbiol. 37:424-428.[CrossRef][Medline]
41 - Wahle, K. W., S. D. Heys, and D. Rotondo. 2004. Conjugated linoleic acids: are they beneficial or detrimental to health? Prog. Lipid Res. 43:553-587.[CrossRef][Medline]
42 - Wallace, R. J., L. C. Chaudhary, N. McKain, N. R. McEwan, A. J. Richardson, P. E. Vercoe, N. D. Walker, and D. Paillard. 2006. Clostridium proteoclasticum: a ruminal bacterium that forms stearic acid from linoleic acid. FEMS Microbiol. Lett. 265:195-201.[CrossRef][Medline]
43 - W
sowska, I., M. R. G. Maia, K. M. Niedzwiedzka, M. Czauderna, J. M. C. Ramalho Ribeiro, E. Devillard, K. J. Shingfield, and R. J. Wallace. 2006. Influence of fish oil on ruminal biohydrogenation of C18 unsaturated fatty acids. Br. J. Nutr. 95:1199-1211.[CrossRef][Medline]
Journal of Bacteriology, March 2007, p. 2566-2570, Vol. 189, No. 6
0021-9193/07/$08.00+0 doi:10.1128/JB.01359-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
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