Alterations in intestinal microbiota composition are associated with several chronic conditions, including obesity and inflammatory diseases. The microbiota of older people displays greater inter-individual variation than that of younger adults. Here we show that the faecal microbiota composition from 178 elderly subjects formed groups, correlating with residence location in the community, day-hospital, rehabilitation or in long-term residential care. However, clustering of subjects by diet separated them by the same residence location and microbiota groupings. The separation of microbiota composition significantly correlated with measures of frailty, co-morbidity, nutritional status, markers of inflammation and with metabolites in faecal water. The individual microbiota of people in long-stay care was significantly less diverse than that of community dwellers. Loss of community-associated microbiota correlated with increased frailty. Collectively, the data support a relationship between diet, microbiota and health status, and indicate a role for diet-driven microbiota alterations in varying rates of health decline upon ageing.

Aims: To assess strains of Lactobacillus, Lactococcus, Pediococcus and Bifidobacterium for their ability to produce the health-promoting fatty acid conjugated linoleic acid (CLA) from free linoleic acid. Methods and Results: In this study, strains of Lactobacillus, Lactococcus, Pediococcus and Bifidobacterium were grown in medium containing free linoleic acid. Growth of the bacteria in linoleic acid and conversion of the linoleic acid to CLA was assessed. Of the bacteria assessed, nine strains of Bifidobacterium produced the c9, t11 CLA isomer from free linoleic acid. The t9, t11 CLA isomer was also produced by some strains, but at much lower concentrations. Conclusions: The production of CLA by bifidobacteria exhibited considerable interspecies variation. Bifidobacterium breve and B. dentium were the most efficient CLA producers among the range of strains tested, with B. breve converting up to 65% linoleic acid to c9, t11 CLA when grown in 0AE55 mg ml )1 linoleic acid. Strains also varied considerably with respect to their sensitivity to linoleic acid. Significance and Impact of the Study: The production of CLA by probiotic bifidobacteria offers a possible mechanism for some health-enhancing properties of bifidobacteria and provides novel opportunities for the development of functional foods.

These results are consistent with the concept that the metabolome is a composite of host and microbe metabolic activity and that the influence of the microbiota on host fatty acid composition can be manipulated by oral administration of CLA-producing microorganisms.

No abstract

The conjugative 63-kb lactococcal plasmid pMRC01 encodes bacteriophage resistance and production of and immunity to a novel broad-spectrum bacteriocin, designated lacticin 3147 (M. P. Ryan, M. C. Rea, C. Hill, and R. P. Ross, Appl. Environ. Microbiol. 62:612-619, 1996). The phage resistance is an abortive infection mechanism which targets the phage-lytic cycle at a point after phage DNA replication. By using the genetic determinants for bacteriocin immunity encoded on the plasmid as a selectable marker, pMRC01 was transferred into a variety of lactococcal starter cultures to improve their phage resistance properties. Selection of resulting transconjugants was performed directly on solid media containing the bacteriocin. Since the starters exhibited no spontaneous resistance to the bacteriocin as a selective agent, this allowed the assessment of the transfer of the naturally occurring plasmid into a range of dairy starter cultures. Results demonstrate that efficient transfer of the plasmid was dependent on the particular recipient strain chosen, and while highfrequency transfer (10 ؊3 per donor) of the entire plasmid to some strains was observed, the plasmid could not be conjugated into a number of starters. In this study, transconjugants for a number of lactococcal starter cultures which are phage resistant and bacteriocin producing have been generated. This bacteriocin-producing phenotype allows for control of nonstarter flora in food fermentations, and the phage resistance property protects the starter cultures in industry. The 63-kb plasmid was also successfully transferred into Lactococcus lactis MG1614 cells via electroporation.

In this study, we assessed the ability of six strains of bifidobacteria (previously shown by us to possess the ability to convert linoleic acid to c9, t11-conjugated linoleic acid (CLA) to grow in the presence of alpha-linolenic acid and to generate conjugated isomers of the fatty acid substrate during fermentation for 42 h. The six strains of bifidobacteria were grown in modified MRS (mMRS) containing alpha-linolenic acid for 42 h at 37 degrees C, after which the fatty acid composition of the growth medium was assessed by gas liquid chromatography (GLC). Indeed, following fermentation of one of the strains, namely Bifidobacterium breve NCIMB 702258, in the presence of 0.41 mg/ml alpha-linolenic acid, 79.1% was converted to the conjugated isomer, C18:3 c9, t11, c15 conjugated alpha-linolenic acid (CALA). To examine the inhibitory effect of the fermented oils produced, SW480 colon cancer cells were cultured in the presence of the extracted fermented oil (10-50 microg/ml) for 5 days. The data indicate an inhibitory effect on cell growth (p

The impact of antibiotic therapy on the intestinal microbiota in the elderly should be considered for long-term health effects, and differential susceptibility may require the development of products (e.g. prebiotics and probiotics) for at-risk subjects.

Bifidobacterium breve species of human intestinal origin have the ability to synthesize cis-9, trans-11 (c9, t11) conjugated linoleic acid (CLA) from free linoleic acid. In this study, the ability of Bifidobacterium species to isomerize C(18) polyunsaturated fatty acids was investigated, and the antiproliferative activities of the two main microbially produced CLA isomers were assessed. Linoleic acid was converted principally to c9, t11 CLA and lesser amounts of t9, t11 CLA, whereas c9, t11 CLA was converted mainly to t9, t11 CLA. Likewise, t10, c12 CLA was converted principally to t9, t11 CLA, which was incorporated into the bacterial cell membranes. To examine the antiproliferative effect of the two main CLA isomers formed, SW480 and HT-29 human colon cancer cells were cultured in the presence of c9, t11 CLA and t9, t11 CLA. The t9, t11 CLA had a more potent antiproliferative effect than c9, t11 CLA. It is tempting to suggest that the ability of Bifidobacterium to produce such bioactive metabolites may be associated with the beneficial effects of bifidobacteria present in the human gastrointestinal tract.