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Featured researches published by Gérard Fonty.


Microbiology | 1987

Establishment of the Microflora and Anaerobic Fungi in the Rumen of Lambs

Gérard Fonty; Philippe Gouet; Jean-Pierre Jouany; Jean Senaud

SUMMARY: The establishment of different bacterial populations and fungi in the rumen was investigated in lambs reared under different conditions of diet and management. The rumen was rapidly colonized by an abundant microflora after birth. By day 2 strictly anaerobic bacteria predominated (109c.f.u. ml−1); their population increased slightly during the first week of life and again when the animals began to ingest solid feed (3 weeks). The composition of the microflora in the 2-10-d-old lambs was quite different from that of adult sheep. The aerobic and facultatively anaerobic bacterial count was 10-100-fold lower than the strictly anaerobic count during the first week, and decreased steadily afterwards. In flock-reared lambs, cellulolytic and methanogenic bacteria appeared very early after birth (3-4 d). At the end of the first week the population of these bacteria reached a level close to that generally observed in a mature rumen. The cellulolytic bacteria were also able to survive in the rumen of lambs fed cows milk exclusively. Anaerobic fungi appeared later (8-10 d). They were present in all lambs studied until 3 weeks of age, and then disappeared in most of them when a solid diet was given.


Applied and Environmental Microbiology | 2005

Anaerobic Microbial Communities in Lake Pavin, a Unique Meromictic Lake in France

Anne-C. Lehours; Corinne Bardot; Aurélie Thénot; Didier Debroas; Gérard Fonty

ABSTRACT The Bacteria and Archaea from the meromictic Lake Pavin were analyzed in samples collected along a vertical profile in the anoxic monimolimnion and were compared to those in samples from the oxic mixolimnion. Nine targeted 16S rRNA oligonucleotide probes were used to assess the distribution of Bacteria and Archaea and to investigate the in situ occurrence of sulfate-reducing bacteria and methane-producing Archaea involved in the terminal steps of the anaerobic degradation of organic material. The diversity of the complex microbial communities was assessed from the 16S rRNA polymorphisms present in terminal restriction fragment (TRF) depth patterns. The densities of the microbial community increased in the anoxic layer, and Archaea detected with probe ARCH915 represented the largest microbial group in the water column, with a mean Archaea/Eubacteria ratio of 1.5. Terminal restriction fragment length polymorphism (TRFLP) analysis revealed an elevated archaeal and bacterial phylotype richness in anoxic bottom-water samples. The structure of the Archaea community remained rather homogeneous, while TRFLP patterns for the eubacterial community revealed a heterogeneous distribution of eubacterial TRFs.


Applied and Environmental Microbiology | 2007

Establishment and development of ruminal hydrogenotrophs in methanogen-free lambs

Gérard Fonty; Keith N. Joblin; Michel Chavarot; Remy Roux; Graham E. Naylor; Fabien Michallon

ABSTRACT The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid concentrations for lambs lacking ruminal methanogens were lower but not markedly dissimilar from those for conventional lambs reared on the same diet. A high population density (107 to 108 cells g−1) of ruminal acetogens slowly developed in methanogen-free lambs. Sulfate- and fumarate-reducing bacteria were present, but their population densities were highly variable. In methanogen-free lambs, the hydrogen capture from fermentation was low (28 to 46%) in comparison with that in lambs containing ruminal methanogens (>90%). Reductive acetogenesis was not a significant part of ruminal fermentation in conventional lambs but contributed 21 to 25% to the fermentation in methanogen-free meroxenic animals. Ruminal H2 utilization was lower in lambs lacking ruminal methanogens, but when a methanogen-free lamb was inoculated with a methanogen, the ruminal H2 utilization was similar to that in conventional lambs. H2 utilization in lambs containing a normal ruminal microflora was age dependent and increased with the animal age. The animal age effect was less marked in lambs lacking ruminal methanogens. Addition of fumarate to rumen contents from methanogen-free lambs increased H2 utilization. These findings provide the first evidence from animal studies that reductive acetogens can sustain a functional rumen and replace methanogens as a sink for H2 in the rumen.


Applied and Environmental Microbiology | 2006

Depth-Related Gradients of Viral Activity in Lake Pavin

Jonathan Colombet; Télesphore Sime-Ngando; H. M. Cauchie; Gérard Fonty; L. Hoffmann; G. Demeure

ABSTRACT High-resolution vertical sampling and determination of viral and prokaryotic parameters in a deep volcanic lake shows that in the absence of thermal stratification but within light, oxygen, and chlorophyll gradients, host availability empirically is prevalent over the physical and chemical environments and favors lytic over lysogenic “viral life cycles.”


Microbiology | 1993

Inhibition of the cellulolytic activity of Neocallimastix frontalis by Ruminococcus flavefaciens

Annick Bernalier; Gérard Fonty; Frédérique Bonnemoy; Philippe Gouet

A study was made of the antagonistic effect of Ruminococcus flavefaciens on the cellulolytic activity of Neocallimastix frontalis. An extracellular factor inhibiting the cellulolytic activity of the fungus was detected in the bacterial supernatant. The antagonistic factor, which precipitated with ammonium sulphate at 40% saturation, was temperature-sensitive and was destroyed at temperatures above 60 degrees C. After separation by anion-exchange chromatography, sequential precipitation, dialysis and SDS-PAGE, two protein species of 100 and 24 kDa were identified as being involved in this antagonistic effect. It is known whether the proteins are two subunits of a single protein or represent two different proteins. The inhibitory factor, which is not a bacterial cellulase, did not affect fungal growth, but it inhibited the activity of the fungal cellulases.


Applied and Environmental Microbiology | 2010

Influence of the Composition of the Cellulolytic Flora on the Development of Hydrogenotrophic Microorganisms, Hydrogen Utilization, and Methane Production in the Rumens of Gnotobiotically Reared Lambs

Frédérique Chaucheyras-Durand; Sébastien Masséglia; Gérard Fonty; Evelyne Forano

ABSTRACT We investigated the influence of the composition of the fibrolytic microbial community on the development and activities of hydrogen-utilizing microorganisms in the rumens of gnotobiotically reared lambs. Two groups of lambs were reared. The first group was inoculated with Fibrobacter succinogenes, a non-H2-producing species, as the main cellulolytic organism, and the second group was inoculated with Ruminococcus albus, Ruminococcus flavefaciens, and anaerobic fungi that produce hydrogen. The development of hydrogenotrophic bacterial communities, i.e., acetogens, fumarate and sulfate reducers, was monitored in the absence of methanogens and after inoculation of methanogens. Hydrogen production and utilization and methane production were measured in rumen content samples incubated in vitro in the presence of exogenous hydrogen (supplemented with fumarate or not supplemented with fumarate) or in the presence of ground alfalfa hay as a degradable substrate. Our results show that methane production was clearly reduced when the dominant fibrolytic species was a non-H2-producing species, such as Fibrobacter succinogenes, without significantly impairing fiber degradation and fermentations in the rumen. The addition of fumarate to the rumen contents stimulated H2 utilization only by the ruminal microbiota inoculated with F. succinogenes, suggesting that these communities could play an important role in fumarate reduction in vivo.


Animal Feed Science and Technology | 1991

Cellulose degradation by two rumen anaerobic fungi in monoculture or in coculture with rumen bacteria.

Annick Bernalier; Gérard Fonty; Ph. Gouet

Abstract Cellulose (Whatman filter paper No. 1) degradation and fermentation by the rumen fungi, Piromonas communis strain FL and Sphaeromonas communis strain FG10, have been investigated. The amount of cellulose degraded by pure fungal cultures and by an association of fungi with either the fermentative bacterium Selenomonas ruminantium strain WPL or the methanogen Methanobrevibacter ruminantium (D.S.M. 1093) was measured. In pure culture, Piromonas communis FL degraded cellulose more efficiently than Sphaeromonas communis . The association of Piromonas communis with Selenomonas ruminantium depressed the cellulolytic activity of the fungus. By contrast, the coculture Sphaeromonas communis—Selenomonas ruminantium was more efficient in the breakdown of filter paper than was the monoculture of Sphaeromonas communis . The cellulolytic activity of Sphaeromonas communis was increased by the presence of Methanobrevibacter ruminantium . In coculture with Piromonas communis , the bacterium had a limited effect, probably because the fungal strain used was itself able to degrade cellulose very rapidly. The metabolism of Piromonas communis and Sphaeromonas communis was shifted towards acetate production with a concomitant decrease in lactate and ethanol production. Assay of protein indicated that the fungal biomass increased in the presence of the methanogen.


Geomicrobiology Journal | 2009

Diversity of Culturable Bacteria, from the Anaerobic Zone of the Meromictic Lake Pavin, Able to Perform Dissimilatory-Iron Reduction in Different in Vitro Conditions

Anne-Catherine Lehours; Isabelle Batisson; Annie Guedon; Gilles Mailhot; Gérard Fonty

A culture-dependent study was performed with the aim of assessing the carbon, electron and Fe(III) sources used for the dissimilatory Fe(III) reduction pathway and the diversity of culturable Fe(III)-reducers in the anoxic zone of the meromictic Lake Pavin. This metabolic pathway was investigated in enrichment cultures inoculated with water samples collected at 70 m depth in the anoxic zone of Lake Pavin. Combinations of different media, organic acids, and incubation gas phases were performed. The potential for Fe(III) reduction in the different growth conditions was assessed by measuring the accumulation of Fe(II) overtime. Bacterial community structure was determined in each growth conditions by Temporal Temperature gradient Gel Electrophoresis (TTGE) profiles of 16S rDNA genes and bands of interest in positive enrichments were sequenced. Comparisons of bacterial community structure between growth conditions revealed that the electron donor, the basal media as well as the Fe(III) source yielded to the selection of different bacterial populations, suggesting that Fe(III) reducers occupy different ecological niches in the anoxic zone of Lake Pavin. Facultative Fe(III) reducers, such as fermentative (e.g., Pseudomonas, Clostridium) and sulphate-reducing (e.g., Desulfovibrio sp.) bacteria, were retrieved in enrichments but well-known obligatory Fe(III) reducers (e.g., Geobacter) were not detected. A greater Fe(III) reduction was noted under H2:CO2 gas phase, suggesting that H2 is used as an electron donor for Fe(III) reduction. Acetate was not used as a precursor for this terminal electron-accepting process, and a high Fe(III) reduction was observed with fumarate provided as the electron donor and carbon sources suggesting that this metabolite may be energetically more beneficial for Fe(III)-reducers.


Archives of Microbiology | 2010

Members of candidate divisions OP11, OD1 and SR1 are widespread along the water column of the meromictic Lake Pavin (France)

Guillaume Borrel; Anne-Catherine Lehours; Corinne Bardot; Xavier Bailly; Gérard Fonty

The vertical distribution of OP11, OD1 and SR1 divisions in the oxycline and in the anoxic water column of Lake Pavin, a freshwater permanently stratified mountain lake in France, was determined by temporal temperature gel gradient electrophoresis and 16S rRNA clone libraries. Gradual changes in the community structure were noted in relation to environmental variables along the oxidized/reduced environment. In addition, a separate effort to identify members of these lineages in the oxic mixolimnion identified sequences affiliated to SR1 and OP11 divisions, indicating that they are more widespread than previously expected.


bioRxiv | 2018

Hydrogenotrophic methanogens of the mammalian gut: functionally similar, thermodynamically different. A modelling approach

Rafael Munoz-Tamayo; Milka Popova; Maxence Tillier; D. P. Morgavi; Jean-Pierre Morel; Gérard Fonty; Nicole Morel-Desrosiers

Methanogenic archaea occupy a functionally important niche in the gut microbial ecosystem of mammals. Our purpose was to quantitatively characterize the dynamics of methanogenesis by integrating microbiology, thermodynamics and mathematical modelling. For that, in vitro growth experiments were performed with pure cultures of key methanogens from the human and ruminant gut, namely Methanobrevibacter smithii, Methanobrevibacter ruminantium and Methanobacterium formicium. Microcalorimetric experiments were performed to quantify the methanogenesis heat flux. We constructed an energetic-based mathematical model of methanogenesis. Our model captured efficiently the dynamics of methanogenesis with concordance correlation coefficients of 0.94 for CO2, 0.99 for H2 and 0.97 for CH4. Together, experimental data and model enabled us to quantify metabolism kinetics and energetic patterns that were specific and distinct for each species despite their use of analogous methane-producing pathways. Then, we tested in silico the interactions between these methanogens under an in vivo simulation scenario using a theoretical modelling exercise. In silico simulations suggest that the classical competitive exclusion principle is inapplicable to gut ecosystems and that kinetic information alone cannot explain gut ecological aspects such as microbial coexistence. We suggest that ecological models of gut ecosystems require the integration of microbial kinetics with nonlinear behaviours related to spatial and temporal variations taking place in mammalian guts. Our work provides novel information on the thermodynamics and dynamics of methanogens. This understanding will be useful to construct new gut models with enhanced prediction capabilities and could have practical applications for promoting gut health in mammals and mitigating ruminant methane emissions.

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Philippe Gouet

Institut national de la recherche agronomique

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Corinne Bardot

Blaise Pascal University

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Jean Senaud

Centre national de la recherche scientifique

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Annick Bernalier

Institut national de la recherche agronomique

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Ph. Gouet

Institut national de la recherche agronomique

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Annie Guedon

Centre national de la recherche scientifique

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Télesphore Sime-Ngando

Centre national de la recherche scientifique

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