Presence of Butyrivibrio fibrisolvens in the digestive tract of dogs and cats, and its contribution to butyrate production

Live yeasts enhance fibre degradation in the cow rumen through an increase in plant substrate colonization by fibrolytic bacteria and fungi

AIMS

To monitor the effect of a live yeast additive on feedstuff colonization by targeted fibrolytic micro-organisms and fibre degradation in the cow rumen.

METHODS AND RESULTS

Abundance of adhering fibrolytic bacteria and fungi on feedstuffs incubated in sacco in the cow rumen was quantified by qPCR and neutral detergent fibre (NDF) degradation was measured. Saccharomyces cerevisiae I-1077 (SC) increased the abundance of fibre-associated Fibrobacter succinogenes on wheat bran (WB) and that of Ruminococcus flavefaciens on alfalfa hay (AH) and wheat silage (WS). The greatest effect was observed on the abundance of Butyrivibrio fibrisolvens on AH and soya hulls (SH) (P < 0·001). Fungal biomass increased on AH, SH, WS and WB in the presence of SC. NDF degradation of AH and SH was improved (P < 0·05) with SC supplementation.

CONCLUSIONS

Live yeasts enhanced microbial colonization of fibrous materials, the degree of enhancement depended on their nature and composition. As an effect on rumen pH was not likely to be solely involved, the underlying mechanisms could involve nutrient supply or oxygen scavenging by the live yeast cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

Distribution of this microbial additive could be an interesting tool to increase fibre digestion in the rumen and thereby improve cow feed efficiency.

Understanding the canine intestinal microbiota and its modification by pro-, pre- and synbiotics - what is the evidence?

Interest in the composition of the intestinal microbiota and possibilities of its therapeutic modifications has soared over the last decade and more detailed knowledge specific to the canine microbiota at different mucosal sites including the gut is available. Probiotics, prebiotics or their combination (synbiotics) are a way of modifying the intestinal microbiota and exert effects on the host immune response. Probiotics are proposed to exert their beneficial effects through various pathways, for example production of antimicrobial peptides, enhancing growth of favourable endogenous microorganisms, competition for epithelial colonisation sites and immune‐modulatory functions. Despite widespread use of pro‐, pre‐ and synbiotics, scientific evidence of their beneficial effects in different conditions of the dog is scarce. Specific effects of different strains, their combination or their potential side‐effects have not been evaluated sufficiently. In some instances, in vitro results have been promising, but could not be transferred consistently into in vivo situations. Specific canine gastrointestinal (GI) diseases or conditions where probiotics would be beneficial, their most appropriate dosage and application have not been assessed extensively. This review summarises the current knowledge of the intestinal microbiome composition in the dog and evaluates the evidence for probiotic use in canine GI diseases to date. It wishes to provide veterinarians with evidence‐based information on when and why these products could be useful in preventing or treating canine GI conditions. It also outlines knowledge about safety and approval of commercial probiotic products, and the potential use of faecal microbial transplantation, as they are related to the topic of probiotic usage.

Isolation of a novel strain of Butyrivibrio fibrisolvens that isomerizes linoleic acid to conjugated linoleic acid without hydrogenation, and its utilization as a probiotic for animals

AIM

Isolation of a new strain of Butyrivibrio fibrisolvens possessing great capacity to produce conjugated linoleic acid (CLA) in order to utilize as a probiotic for animals.

METHODS AND RESULTS

A novel strain (MDT-5) was isolated from the goat rumen, which exclusively converted linoleic acid (LA) to CLA, because of its high LA isomerase activity with virtually no CLA reductase activity. MDT-5 also converted linolenic acid to conjugated linolenic acid that may be more bioactive than CLA. The oral administration of MDT-5 every other day to mice for 2 weeks resulted in increased amounts of CLA in the contents of the large intestine (2.5-fold), as well as in adipose tissue (threefold). Feeding a high-LA diet, as well as prolonging the period of MDT-5 administration, further increased the CLA content in body fat.

CONCLUSIONS

MDT-5 has by far greater ability to produce CLA than any other known bacteria. Administration of MDT-5 to mice increases CLA production in the large intestine, which results in increased CLA absorption.

SIGNIFICANCE AND IMPACT OF THE STUDY

MDT-5 may be useful in pet animals as a probiotic to provide CLA continuously.

Diet-dependent shifts in ruminal butyrate-producing bacteria

The influence of a host's diet on Butyrivibrio and Pseudobutyrivibrio populations was investigated by competitive PCR. Specific primers were designed and competitive PCRs developed for both groups. Results (from 4 cows with different diets) suggested that high-fiber intake essentially increases the Butyrivibrio amounts in the rumen, whereas high-energy food additives lead to its suppression. The Pseudobutyrivibrio concentration also changed during the experiment but without any significant relation to the host's diet.

Oral administration of butyrivibrio fibrisolvens, a butyrate-producing bacterium, decreases the formation of aberrant crypt foci in the colon and rectum of mice

Butyrivibrio fibrisolvens, a butyrate-producing ruminal bacterium, was evaluated for use as a probiotic to prevent colorectal cancer. Oral administration to Jcl:ICR mice of a new strain of B. fibrisolvens (MDT-1) that produces butyrate at a high rate (10(9) cfu/dose) increased the rate of butyrate production by fecal microbes, suggesting that MDT-1 can grow in the gut. The number of colorectal aberrant crypt foci (ACF), putative preneoplastic lesions induced by 1,2-dimethylhydrazine, was reduced after MDT-1 administration (10(9) cfu/dose, 3 times/wk for 4 wk). The number of aberrant crypts (ACs), number of foci having 3 or 4 ACs per focus, and the percentage of mice having 3 or 4 ACs per focus were also reduced, suggesting that the progress of lesions was suppressed by MDT-1. Interestingly, the MDT-1 cell homogenate did not have a similar beneficial effect. MDT-1 had low beta-glucuronidase activity, and administration of MDT-1 reduced the beta-glucuronidase activity in the colorectal contents. The numbers of natural killer (NK) and NKT cells in the spleen were markedly enhanced in response to MDT-1. Decreased beta-glucuronidase activity and increased numbers of NK and NKT cells and butyrate production may explain in part why MDT-1 administration suppressed ACF formation. These results suggest that colorectal cancer may be prevented or suppressed by the utilization of MDT-1 as a probiotic. Administration of MDT-1 had no harmful effect on the health of mice at least for 3 mo.

A new strain of Butyrivibrio fibrisolvens that has high ability to isomerize linoleic acid to conjugated linoleic acid

A new strain of Butyrivibrio fibrisolvens (TH1) that has high potential to produce conjugated linoleic acid (CLA) was isolated. Strain TH1 had higher LA isomerase (LA-I) activity, and was much more tolerant to linoleic acid (LA) than other strains examined. However, high CLA reductase (CLA-R) activity resulted in the temporary accumulation of CLA and subsequent conversion to trans-vaccenic acid (t-VA). When LA was added to growing TH1 cultures in a solution with dimethylsulfoxide (LA/DMSO), CLA produced was greater than when LA was added in a mixture with bovine serum albumin (BSA). The number of viable cells decreased upon addition of LA/DMSO, but then increased as the CLA decreased upon its conversion to t-VA. This result suggests that B. fibrisolvens can resume growing by the removal of CLA from the cells. Most CLA was released from B. fibrisolvens cells by gentle washing with BSA, suggesting that CLA bound to the cells might be removed in the rumen and large intestine. Thus, CLA production by B. fibrisolvens in the digestive tract could be increased by a reduction in CLA-R activity without accompanying an overall decrease in the cell number of B. fibrisolvens. Fatty acids (FAs) with 18 carbon backbone inducted LA-I activity, whereas unsaturated FAs induced CLA-R activity, suggesting that FAs stimulate the synthesis of LA-I and CLA-R. Providing a diet with a low ratio of unsaturated to saturated FAs may favor CLA production.

Characterization and transcription of the genes involved in butyrate production in Butyrivibrio fibrisolvens type I and II strains

The genes in Butyrivibrio fibrisolvens that encode the enzymes involved in butyrate production were sequenced. In a type I strain (ATCC 19171(T)), the genes coding for the enzymes that catalyze the conversion from acetyl-CoA to butyryl-CoA, thl (thiolase), crt (crotonase), hbd (beta-hydroxybutyryl-CoA dehydrogenase), bcd (butyryl-CoA dehydrogenase), etfB (electron transfer flavoprotein [ETF]-beta), and etfA (ETF-alpha), were found to be clustered and arranged in this order. A type II strain (ATCC 51255) had the same clustered genes with the same arrangement, except that crt was not present in the clustered genes. The deduced amino acid sequences of these enzymes did not greatly differ between the two strains, and even between B. fibrisolvens and clostridia. Amino acid identity appeared to be higher within the same type than between types I and II. The clustered genes were shown to be cotranscribed, and constitutively transcribed without being affected significantly by culture conditions.

Molecular Characterization and Transcription of the luxS Gene That Encodes LuxS Autoinducer 2 Synthase in Streptococcus bovis

Presence of the luxS gene that encodes LuxS autoinducer 2 (AI-2) synthase in Streptococcus bovis was demonstrated, and the molecular properties and transcription of the gene were examined. The S. bovis luxS was transcribed in a monocistronic fashion. Intracellular luxS-mRNA increased sharply during the initial exponential growth, and decreased abruptly after the middle exponential phase. The large drop in luxS transcription began before the glucose supply to cells decreased or the growth rate declined. Transcription of luxS was not directly related to cell density, and continued at a maximal rate when cells were kept growing at a maximal rate. It is conceivable that AI-2 activity in S. bovis acts as a signal for adjusting cell physiology and metabolism in response to environmental conditions. However, the role of LuxS in S. bovis, including the regulation of AI-2 synthesis,, remains to be clarified.

Production of conjugated linoleic acid by intestinal bacteria in dogs and cats

Production of conjugated linoleic acid (CLA) by the intestinal bacteria of dogs and cats was demonstrated by incubating their feces with linoleic acid (LA). CLA accumulated once, and then decreased with time. The numbers of LA-hydrogenating bacteria in the intestines appeared to decrease greatly with the ages of dogs and cats. As a major product of LA biohydrogenation, trans-vaccenic acid (t-VA) was identified. Most CLA and t-VA were readily solubilized by shaking the incubation mixture with bovine serum albumin, which strongly supports the presumption that CLA and t-VA are mostly formed on the outer surface of cell membrane, or excreted to the outer cell surface. This result suggests that CLA and t-VA can readily be absorbed through the large intestines. Triacylglycerol and phospholipid were shown to be hydrolyzed to free fatty acids by fecal bacteria, which is critical for biohydrogenation to occur, because esterified LA is not hydrogenated. However, since the ability of intestinal bacteria to produce CLA is probably low, it is desirable to augment CLA production.