A genomic perspective on the potential of Actinobacillus succinogenes for industrial succinate production

<p>Abstract</p> <p>Background</p> <p>Succinate is produced petrochemically from maleic anhydride to satisfy a small specialty chemical market. If succinate could be produced fermentatively at a price competitive with that of maleic anhydride, though, it could replace maleic anhydride as the precursor of many bulk chemicals, transforming a multi-billion dollar petrochemical market into one based on renewable resources. <it>Actinobacillus succinogenes </it>naturally converts sugars and CO₂into high concentrations of succinic acid as part of a mixed-acid fermentation. Efforts are ongoing to maximize carbon flux to succinate to achieve an industrial process.</p> <p>Results</p> <p>Described here is the 2.3 Mb <it>A. succinogenes </it>genome sequence with emphasis on <it>A. succinogenes</it>'s potential for genetic engineering, its metabolic attributes and capabilities, and its lack of pathogenicity. The genome sequence contains 1,690 DNA uptake signal sequence repeats and a nearly complete set of natural competence proteins, suggesting that <it>A. succinogenes </it>is capable of natural transformation. <it>A. succinogenes </it>lacks a complete tricarboxylic acid cycle as well as a glyoxylate pathway, and it appears to be able to transport and degrade about twenty different carbohydrates. The genomes of <it>A. succinogenes </it>and its closest known relative, <it>Mannheimia succiniciproducens</it>, were compared for the presence of known Pasteurellaceae virulence factors. Both species appear to lack the virulence traits of toxin production, sialic acid and choline incorporation into lipopolysaccharide, and utilization of hemoglobin and transferrin as iron sources. Perspectives are also given on the conservation of <it>A. succinogenes </it>genomic features in other sequenced Pasteurellaceae.</p> <p>Conclusions</p> <p>Both <it>A. succinogenes </it>and <it>M. succiniciproducens </it>genome sequences lack many of the virulence genes used by their pathogenic Pasteurellaceae relatives. The lack of pathogenicity of these two succinogens is an exciting prospect, because comparisons with pathogenic Pasteurellaceae could lead to a better understanding of Pasteurellaceae virulence. The fact that the <it>A. succinogenes </it>genome encodes uptake and degradation pathways for a variety of carbohydrates reflects the variety of carbohydrate substrates available in the rumen, <it>A. succinogenes</it>'s natural habitat. It also suggests that many different carbon sources can be used as feedstock for succinate production by <it>A. succinogenes</it>.</p

Etude structurale et fonctionnelle de genes homologues a des genes nod de Rhizobium meliloti chez le fixateur d'azote non symbiotique Azospirillum brasilense

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 84422 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Quantification d'un stress viscéral aigu part la mesure de la capacité antioxydante sérique chez le rat

La mise en application de la nouvelle réglementation Européenne concernant l expérimentation animale va entraîner des changements, dès sa transcription en droit Français, notamment par la nécessité d une meilleure prise en compte du bien-être animal. Cette directive, 2010/63/UE, impose l évaluation des projets et procédures, et met l accent sur l importance des point-limites pour éviter tout stress, toute douleur ou détresse des animaux utilisés. L objectif de ce travail a été de quantifier le stress viscéral aigu par la mesure de la capacité antioxydante totale (CAT) sérique. Un modèle d induction d ulcères gastriques chez le rat a été utilisé. La CAT du sérum a été réduite significativement de 12,2% après une chirurgie digestive induisant un stress viscéral aigu (1,08 +/- 0,17 mmol/l, n=21 rats) par rapport à des animaux témoins ne subissant pas la chirurgie digestive (1,23 +/- 0,14 mmol/l, n=20 rats). Nos résultats suggèrent une consommation d antioxydants suite au stress viscéral aigu. Ce paramètre pourrait être utile comme critère permettant d estimer un point limite lors de chirurgie expérimentale.TOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF

L’activité physique comme objet de santé publique : fabrique, diffusion et réception des nouvelles normes de santé active

Sociologie du sport et émergence de l’activité physique La connaissance des pratiques physiques et du sport s’est révélée dans les années 1980 comme étant une « clé de la connaissance de la société » (Elias & Dunning, 1994). Une sociologie du sport s’est ainsi déployée à partir de la reconnaissance du sport comme un « fait social total » comme le définissait l’anthropologue Marcel Mauss (1922), c’est à dire en tant que phénomène « où s’expriment à la fois et d’un coup toutes les institutions ..

Insights into Actinobacillus succinogenes Fermentative Metabolism in a Chemically Defined Growth Medium

Chemically defined media allow for a variety of metabolic studies that are not possible with undefined media. A defined medium, AM3, was created to expand the experimental opportunities for investigating the fermentative metabolism of succinate-producing Actinobacillus succinogenes. AM3 is a phosphate-buffered medium containing vitamins, minerals, NH(4)Cl as the main nitrogen source, and glutamate, cysteine, and methionine as required amino acids. A. succinogenes growth trends and end product distributions in AM3 and rich medium fermentations were compared. The effects of NaHCO(3) concentration in AM3 on end product distribution, growth rate, and metabolic rates were also examined. The A. succinogenes growth rate was 1.3 to 1.4 times higher at an NaHCO(3) concentration of 25 mM than at any other NaHCO(3) concentration, likely because both energy-producing metabolic branches (i.e., the succinate-producing branch and the formate-, acetate-, and ethanol-producing branch) were functioning at relatively high rates in the presence of 25 mM bicarbonate. To improve the accuracy of the A. succinogenes metabolic map, the reasons for A. succinogenes glutamate auxotrophy were examined by enzyme assays and by testing the ability of glutamate precursors to support growth. Enzyme activities were detected for glutamate synthesis that required glutamine or α-ketoglutarate. The inability to synthesize α-ketoglutarate from glucose indicates that at least two tricarboxylic acid cycle-associated enzyme activities are absent in A. succinogenes

Effect of Overexpression of Actinobacillus succinogenes Phosphoenolpyruvate Carboxykinase on Succinate Production in Escherichia coli

Succinate fermentation was investigated in Escherichia coli strains overexpressing Actinobacillus succinogenes phosphoenolpyruvate carboxykinase (PEPCK). In E. coli K-12, PEPCK overexpression had no effect on succinate fermentation. In contrast, in the phosphoenolpyruvate carboxylase mutant E. coli strain K-12 ppc::kan, PEPCK overexpression increased succinate production 6.5-fold