Alain Rimbault

Thermococcus fumicolans sp. nov., a new hyperthermophilic archaeon isolated from a deep-sea hydrothermal vent in the north Fiji Basin.

An extremely thermophilic archaeon, strain ST557T (T = type strain), was isolated from a deep-sea hydrothermal vent in the North Fiji Basin. This strain is a strictly anaerbic coccus whose cells are about 0.8 to 2 microns in diameter. The optimum temperature, pH and sea salt concentration for growth are 85 degrees C, 8.5, and 20 to 40 g/liter, respectively. Strain ST557T grows preferentially in the presence of elemental sulfur on proteinaceous substrates and on a mixture of 20 amino acids. It grows slowly on pyruvate and maltose. Growth is inhibited by rifampin. The DNA G + C content is 54 to 55 mol%. Sequencing of the 16S rRNA gene revealed that strain ST557T belongs to the genus Thermococcus. We propose that this organism should be placed in a new species, Thermococcus fumicolans.

An experimental model of necrotising enterocolitis

Non-enteropathogenic strains of Clostridium butyricum in neonatal necrotising enterocolitis (NEC) were discussed in The Lancet 20 years ago. The role of C butyricum as a primary pathogen gave rise to controversy because it does not produce any specific toxin and occurs in both healthy infants and those with NEC. The gut of premature neonates is immature and colonised with few bacteria, and Gregor Lawrence and colleagues postulated that in such infants a non-pathogen, with few or no competitors, is able to multiply without interference. Thus, bacterial metabolites, which are overproduced, may be absorbed and cause mucosal damage, thus initiating NEC. The investigators suggested that gnotobiotic animal models may be useful since a single or a few bacterial strains colonise the gut to high levels even if they are not pathogens. Birds, unlike newborn mammals, do not have endogenous intestinal lactase, a situation which mimics the lactase A. Calculation of CTCL-SI

Synthesis of 2-hydroxy acid from 2-amino acid by Clostridium butyricum.

Cultures of Clostridium butyricum type strain in synthetic medium supplemented with various L-2-amino acids revealed the presence of the corresponding 2-hydroxy acid. This metabolite is able to produce the polyester poly(2-hydroxyalkanoic acid). The bioconversion is not stereoselective since D-2-amino acids were also converted. Chiral GC analysis demonstrated that only D-enantiomer is formed from L-leucine.

Cleavage of L-leucine-containing dipeptides by Clostridium butyricum.

The ability of Clostridium butyricum cultures to hydrolyze three L-leucine-containing dipeptides (Leu-Leu, Leu-Gly and Gly-Leu) in a synthetic minimal medium is demonstrated by using gas chromatography coupled with mass spectrometry. The 13C nuclear magnetic resonance and a labeled dipeptide L-[1-13C]Leu-Gly were used to confirm this activity.

Organic acids and stable isotope metabolic studies of a thermophilic sulfur-dependent anaerobic archaeon

Abstract Organic acids were analyzed as tert -butyldimethylsiyl derivatives by gas chromatography and gas chromatography-mass spectrometry in cultures of an extremely thermophilic sulfur-dependent anaerobic archaeon. strain ST 546, isolated from a deep-sea hydrothermal vent. Quantitative data indicate the formation of propanoic, 2-methylpropanoic, 3-(methylthio)propanoic, phenylacetic, 4-hydroxyphenylacetic and indole-3-acetic acids (all detected at the millimolar level) and one compound tentatively identified to 2- and/or 3 methylbutanoic acid in peptone media. In addition to these compounds, formic and 2-hyroxypropanoic acids (all the acids detected at the sub-millimolar level) along with another compound are associated with the 20 amino-acid containing medium culture. Use of stable-isotope labelled amino acids demonstrated that 3-(methylthio)propanoic acid originates from L -methionine whereas L -phenylalanine yields phenylacetic acid, but not 4-hydroxyphenylacetic acid.

Synthesis and polymerization of benzyl (3R,4R)-3-methylmalolactonate via enzymatic preparation of the chiral precursor.

beta-methylaspartate ammonia-lyase, EC 4.3.1.2, (beta-methylaspartase) from Clostridium tetanomorphum was used to produce a 40/60 molar ratio of (2S,3R) and (2S,3S)-3-methylaspartic acids, 2a and 2b, respectively, from mesaconic acid 1 as substrate, on a large scale. To prepare (3R,4R)-3-methyl-4-(benzyloxycarbonyl)-2-oxetanone (benzyl 3-methylmalolactonate) 6, 2a and 2b were transformed, in the first step, into 2-bromo-3-methylsuccinic acids 3a and 3b and separated. After three further steps, (2S,3S)-3a yielded the alpha, beta-substituted beta-lactone (3R,4R) 6 with a very high diastereoisomeric excess (> 95% by chiral gas chromatography). The corresponding crystalline polymer, poly[benzyl beta-(2R,3S)-3-methylmalate] 8, prepared by an anionic ring opening polymerization, was highly isotactic as determined by 13C NMR. Catalytic hydrogenolysis of lactone 6 yielded (3R,4R)-3-methyl-4-carboxy-2-oxetanone (3-methylmalolactonic acid) 7, to which reactive, chiral, or bioactive molecules can be attached through ester bonds leading to polymers with possible therapeutic applications. Because of the ability of beta-methylaspartase to catalyse both syn- and anti-elimination of ammonia from (2S,3RS)-3-methylaspartic acid 2ab at different rates, the (2S,3R)-stereoisomer 2a was retained and isolated for further reactions. These results permit the use of the chemoenzymatic route for the preparation of both optically active and racemic polymers of 3-methylmalic acid with well-defined enantiomeric and diastereoisomeric compositions.

Phenotypic Differentiation between Clostridium hastiforme and Clostridium subterminale by Headspace Gas Chromatography

Assessment of methane and methanethiol in the headspace gas from cultures of various strains labeled Clostridium hastiforme or Clostridium subterminale allowed differentiation between these two species. C. hastiforme strains produced significantly more methane and less methanethiol than C. subterminale strains. We confirm that strain DSM 1786 (= ATCC 25772) does not belong to either of these species.

Trace Methane in Some Proteolytic Nonglucidolytic Clostridia: The Role of Some S-Methyl and N-Methyl Compounds

Clostridia form a very heterogeneous bacterial group involved in the various aspects of the decomposition of organic matter1–3. The reduction into methane of various substrates 4–8 formed in the prior steps by members of microbial communities, e.g., Clostridia1,2,9 is carried out by methanogens.