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J Doré

Publications and source records attributed to J Doré.

29 records · Page 2Linked to original sources
PubMed1998

Design and evaluation of a 16S rRNA-targeted oligonucleotide probe for specific detection and quantitation of human faecal Bacteroides populations.

Colonic Bacteroides include several species which, by their population level and activities, are significant contributers to the metabolic activity and health of man and animals. Yet, the understanding of their ecology has been hampered by the lack of highly specific and reliable enumeration techniques. Based on 16S rRNA sequence comparisons within the available database, we have designed an 18-mer oligonucleotide that targets a region common to-and specific for the Bacteroides-Porphyromonas-Prevotella group. We have tested the specificity of the probe and its usefulness for studies of human faecal samples. Under experimentally optimized hybridization conditions, the probe was shown to similarly recognize the rDNA obtained from 40 strains representing 8 species of the Bacteroides-Porphyromonas-Prevotella group. Importantly, it did not recognize 31 strains of microorganisms representing 8 genera of the dominant human faecal microbiota. Among selected colonies of dominant microorganisms of the faecal flora of two human individuals, strains identified as B. vulgatus by immunoblots using a species-specific monoclonal antibody were all detected by the probe. Colony hybridization was used to enumerate total Bacteroides-group microorganisms in faecal specimen from children and adults. The probe described therein was further used in quantitative RNA blots to monitor fluctuations of the Bacteroides-group versus Bifidobacterium genus in frozen faecal samples from a child between 85 and 125 days of age. It will be applicable to similar investigations of other anaerobic environments.

Adult↗
PubMed1996

Diversity of H2/CO2-utilizing acetogenic bacteria from feces of non-methane-producing humans.

The purpose of this work was to study H2/CO2-utilizing acetogenic population in the colons of non-methane-producing individuals harboring low numbers of methanogenic archaea. Among the 50 H2-consuming acetogenic strains isolated from four fecal samples and an in vitro semi-continuous culture enrichment, with H2/CO2 as sole energy source, 20 were chosen for further studies. All isolates were Gram-positive strict anaerobes. Different morphological types were identified, providing evidence of generic diversity. All acetogenic strains characterized used H2/CO2 to form acetate as the sole metabolite, following the stoichiometric equation of reductive acetogenesis. These bacteria were also able to use a variety of organic compounds for growth. The major end product of glucose fermentation was acetate, except for strains of cocci that mainly produced lactate. Yeast extract was not necessary, but was stimulatory for growth and acetogenesis from H2/CO2.

Acetates↗
PubMed1995

Most probable number enumeration of H2-utilizing acetogenic bacteria from the digestive tract of animals and man.

A method is proposed that allows the enrichment and most probable number estimation of H2/CO2(-)utilizing acetogenic bacteria. It is based on the difference in acetate production for serial dilutions incubated under either a test H2/CO2 (4:1), or a control N2/CO2 (4:1) headspace atmosphere. A nutritionally non-selective medium was used, containing bromoethane-sulfonic acid as inhibitor of methanogenic archaea and 10% pre-incubated clarified rumen fluid. Acetogenic bacteria were enumerated in rumen and hindgut contents of animals and in human feces. They ranged from below 10(2) to above 10(8) per gram wet weight gut content and their population levels were the highest in the absence of methanogenesis. The method described therein should prove useful to better understand the diversity and ecological importance of dominant gut acetogens.

Acetates↗
PubMed1995

Isolation and characterization of a new hydrogen-utilizing bacterium from the rumen.

A new H2/CO2-utilizing acetogenic bacterium was isolated from the rumen of a mature deer. This is the first report of a spore-forming Gram-negative bacterial species from the rumen. The organism was a strictly anaerobic, motile rod and was able to grow autotrophically on hydrogen and carbon dioxide. Acetate was the major product detected. Glucose, fructose and lactate were also fermented heterotrophically. The optimum pH for growth was 7.0-7.5, and the optimum temperature was 37-42 degrees C. Yeast extract was required for growth and rumen fluid was highly stimulatory. The DNA base ratio was 52.9 +/- 0.5 mol% G+C. On the basis of these characteristics and fermentation products, the isolate was considered to be different from acetogenic bacteria described previously.

Animals↗
PubMed1992

Interrelations between populations of methanogenic archaea and sulfate-reducing bacteria in the human colon.

In humans, CH4 is produced in the colon by methanogenic archaea and is detected in breath samples from approximately 50% of healthy adults, identified as CH4-excretors. Methanogenesis and sulfate reduction have been described as two mutually exclusive processes, potentially regulated by sulfate availability. To determine whether microbial population balances reflected these apparently co-regulated activities, we compared sulfate-reducing bacteria, methanogenic archaea, sulfate and sulfide concentrations in faeces of 10 CH4-excretors (CH4+) and 9 non-CH4-excretors (CH4-). The mean +/- SE of the logarithm of methanogenic archaea per gram wet weight were 9.0 +/- 0.2 and 4.0 +/- 0.7 for CH4+ and CH4-, respectively (P < 0.001). Sulfate-reducing bacterial counts were 6.5 +/- 0.1 and 7.3 +/- 0.2, respectively (P < 0.001). Fecal sulfate and sulfide concentrations did not differ between groups. These results suggest that a competitive interrelation between methanogenic archaea and sulfate-reducing bacteria occurs in the human colon. However, it does not lead to a complete exclusion of the two populations.

Adolescent↗
PubMed1990

Metabolism of One-Carbon Compounds by the Ruminal Acetogen Syntrophococcus sucromutans.

Syntrophococcus sucromutans is the predominant species capable of O demethylation of methoxylated lignin monoaromatic derivatives in the rumen. The enzymatic characterization of this acetogen indicated that it uses the acetyl coenzyme A (Wood) pathway. Cell extracts possess all the enzymes of the tetrahydrofolate pathway, as well as carbon monoxide dehydrogenase, at levels similar to those of other acetogens using this pathway. However, formate dehydrogenase could not be detected in cell extracts, whether formate or a methoxyaromatic was used as electron acceptor for growth of the cells on cellobiose. Labeled bicarbonate, formate, [1-C] pyruvate, and chemically synthesized O-[methyl-C]vanillate were used to further investigate the catabolism of one-carbon (C(1)) compounds by using washed-cell preparations. The results were consistent with little or no contribution of formate dehydrogenase and pointed out some unique features. Conversion of formate to CO(2) was detected, but labeled formate predominantly labeled the methyl group of acetate. Labeled CO(2) readily exchanged with the carboxyl group of pyruvate but not with formate, and both labeled CO(2) and pyruvate predominantly labeled the carboxyl group of acetate. No CO(2) was formed from O demethylation of vanillate, and the acetate produced was position labeled in the methyl group. The fermentation pattern and specific activities of products indicated a complete synthesis of acetate from pyruvate and the methoxyl group of vanillate.

Journal Article↗
PubMed1990

[O-demethylation and metabolism of the methoxyl group of vanillic acid, monomer model of lignin, by the rumen bacterium Syntrophococcus sucromutans].

The O-demethylation of a lignin monomer by washed cells of the rumen bacterium S sucromutans was studied using chemically synthesized O-[methyl-14C]vanillate. During cometabolism of pyruvate and vanillate, the label from the methoxyl group was incorporated into acetate, the sole product, which was singly labeled in the methyl group.

Animals↗
PubMed1989

Lipid growth requirement and influence of lipid supplement on fatty acid and aldehyde composition of Syntrophococcus sucromutans.

Results concerning the ruminal fluid growth requirement of the ruminal acetogen, Syntrophococcus sucromutans, indicate that octadecenoic acid isomers satisfy this essential requirement. Complex lipids, such as triglycerides and phospholipids, can also support growth. The cellular fatty acid and aldehyde composition closely reflects that of the lipid supplement provided to the cells. Up to 98% of the fatty acids and 80% of the fatty aldehydes are identical in chain length and degree of unsaturation to the octadecenoic acid supplement provided in the medium. S. sucromutans shows a tendency to have a greater proportion of the aldehyde form among its 18 carbon chains than it does with the shorter-chain simple lipids, which may be interpreted as a strategy to maintain membrane fluidity. 14C labeling showed that most of the oleic acid taken up from the medium was incorporated into the membrane fraction of the cells.

Aldehydes↗
PubMedDate not supplied

Acetogenic coccoid spore-forming bacteria isolated from the rumen.

Thirteen strains of a new acetogenic bacterium were isolated from the rumen contents of lambs, llamas and bisons. This paper is the first report of Gram-positive coccoid spore-forming bacteria occurring in chains and able to use H2 + CO2 as energy source and produce acetate from this gas mixture. One of them, chosen as the reference strain for its efficiency in utilizing H2/CO2 likely via the acetyl-CoA pathway, was characterized in detail. The G + C ratio of the DNA of the organism was 46.5 mol%. The temperature and pH optimum were 37 degrees-40 degrees C and 6.3-6.8, respectively. Numerous organic substrates including some o-methylate aromatic compounds were used heterotrophically. The full 16S rRNA gene sequence was determined. The phylogeny, physiology, morphology and numerous features described here are sufficiently different from those of any bacteria described today to justify the definition of a new species. The name "New acetogenic bacterium" is temporarily proposed, awaiting a future taxonomic revision of the genus Clostridium.

Acetic Acid↗
PubMedDate not supplied

Selective in vitro degradation of the sialylated fraction of germ-free rat mucins by the caecal flora of the rat.

Mucins, which are synthesized throughout the gastrointestinal tract, may be degraded by the microflora of the large intestine. The present study was undertaken to determine the differential fate of the various types of mucins. Mucins from germ-free rats were incubated in vitro in the presence of whole caecal flora from the conventional rat. Neutral, acidic and acidic sulphated mucins were spectrophotometrically assayed over time upon anaerobic incubation. Sialylated mucins were more rapidly degraded (90%) than the other two types after 1 h and almost completely within 4 h. Neutral and acidic sulphated mucins, with a 10-fold and 30-fold lower content than the sialylated fraction in the original substrate, were more slowly degraded and to a lesser extent within 4 h, (55 and 40%, respectively). The method used in the present study made it possible to investigate the activity of gut bacteria towards the various types of mucins. The degradation of the three mucin types was not uniform, the highest rate and extent of degradation being observed for sialylated mucins.

Animals↗