Jean Pierre Touzel

Isolation and Characterization of a New Thermophilic Methanosarcina, the Strain CHTI 55

Summary A new thermophilic, acetoclastic methanogen (strain CHTI 55) was isolated from enrichment cultures on sodium acetate from a bench scale digester treating a mixture of solid wastes at 55 °C. Morphologically, the strain has the characteristic appearance of Methanosarcina but it forms very large aggregates and coccoid units which are released from the clumps of organisms in old cultures. The isolate uses acetate, methanol, methylamines but neither H2+CO2 nor formate for growth and methane production. Growth of strain CHTI 55 occured throughout a pH range between 6.5 and 8 and at temperatures ranging from 35 °C to 63 °C. The maximal growth rate on acetate (0.085 h-1) was at pH 6.8 and 57°C. The affinity constant for acetate and cell yield were 9.6 mM and 1.4 g/mol, respectively. The G + C content of DNA was 39.3 mol%.

Molecular characterization of the glutathione peroxidase gene of the human malaria parasite Plasmodium falciparum

In this paper we report the isolation and the characterization of a gene encoding the antioxidant enzyme glutathione peroxidase from the human malaria parasite Plasmodium falciparum. This gene contains two introns of 208 and 168 bp and is present in a single copy on chromosome 13. The open reading frame encodes a protein with a predicted length of 205 amino acids, which possesses a potential cleavage site between residues 21 and 22 after a hydrophobic region with the characteristics of a signal sequence. Therefore, the mature protein is predicted to be 184 residues long with a molecular mass of 21404 Da. In comparison with other known glutathione peroxidases many amino acid residues implicated in catalysis are conserved in the malarial enzyme. Phylogenetic analysis indicates that the deduced protein sequence is more closely related to plant glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase. A 1.5-kb transcript was identified in asynchronous erythrocytic stages.

Clostridium neopropionicum sp. nov., a strict anaerobic bacterium fermenting ethanol to propionate through acrylate pathway

Strain X4 was isolated several years ago from an anaerobic mesophilic plant treating vegetable cannery waste waters. It was the first example of propionic fermentation from ethanol. Morphologic and physiologic characterizations of the strain are presented here. This strain is described as type strain of a new species, Clostridium neopropionicum sp. nov. Whole cells of strain X4 ferment [1-13C]ethanol and CO2 to [2-13C]propionate, [1-13C]acetate and [2-13C]propanol, suggesting the absence of a randomizing pathway during the propionate formation. Enzymes involved in this fermentation were assayed in cell-free extracts of cells grown with ethanol as sole substrate. Alcohol dehydrogenase, aldehyde dehydrogenase, phosphate acetyl transferase, acetate kinase, pyruvate synthase, lactate dehydrogenases, and the enzymes of the acrylate pathway were detected at activities sufficient to be involved in ethanol fermentation. The same pathway may be used for the degradation of lactate or acrylate to acetate.

Description of a New Strain of Methanothrix soehngenii and Rejection of Methanothrix concilii as a Synonym of Methanothrix soehngenii

A new mesophilic strain of Methanothrix, strain FE, was highly purified from the sludge of an anaerobic digester after enrichment on sodium acetate and is described. Strain FE was compared with other strains of Methanothrix, Methanothrix soehngenii strain OpfikonT (= DSM 2139T) (T = type strain) and Methanothrix concilii strain GP6T (= DSM 3671T). The differences within the strains were mainly related to their requirement for yeast extract. The three strains were found to be similar in their deoxyribonucleic acid guanine-plus-cytosine contents (50.2 to 52.6 mol%) and showed 100% deoxyribonucleic acid-deoxyribonucleic acid homology. For these reasons we propose to recognize synonymy, reject the name Methanothrix concilii Patel 1985, 35:223, and assign this organism to the species Methanothrix soehngenii Huser, Wuhrmann and Zehnder 1983, 33:439.

Paenibacillus marinum sp. nov., a thermophilic xylanolytic bacterium isolated from a marine hot spring in Tunisia

Among a large collection of Tunisian hot springs bacterial isolates a bacterial strain, THE22T, with xylanolytic properties was identified. The bacterium was isolated from a natural hot spring “Ain Echefa” at Mediteranean sea (Korbous, North‐Eastern Tunisia). The novel strain was Gram positive, spore‐forming, rod‐shaped, facultatively anaerobic and grew optimally under conditions of 55 °C, 1% (w/v) NaCl and pH 7–8. The 16S rRNA gene sequence analysis showed that strain THE22T fell within the radiation of the cluster comprising Paenibacillus species with Paenibacillus phyllosphaerae PALXIL04T as the closest phylogenetic neighbour (95.8%). The predominant components in the fatty methyl ester profile were iso‐C16:0 (34.46%), C16:0 (19.64%), anteiso‐C15:0 (19.18%) and anteiso‐C17:0 (18.11%). The major respiratory quinone was menaquinone‐7 (MK‐7). The diamino acid found in the cell‐wall peptidoglycan was meso‐diaminopimelic acid. The base composition of DNA was 56 mol%. Based on the polyphasic taxonomic data, strain THE‐22T (=DSM 18499T = LMG 23758T) was recognized as a novel species within the genus Paenibacillus. The name Paenibacillus marinum sp. nov. is proposed.

Isolation and characterization of a thermophilic Methanobacterium able to use formate, the strain FTF

A thermophilic anaerobic which produced methane from formate and H2 and CO2 was isolated from a bench-scale digester treating a mixture of solid wastes at 55°C, after enrichment cultures on sodium acetate. The cells were slightly crooked rods occurring singly or in filaments. The bacterium was not motile, and stained Gram positive. Colonies appearing after 1 week of incubation were white with filamentous edges and 1 mm in diameter. The organism used H2:CO2 or formate as an energy source. Yeast extract was not required but stimulated growth significantly. Casamino acids were stimulatory and could serve as a nitrogen source. Cysteine was used as a sulfur source. The optimum pH for growth was 7.5. Growth occurred from 35 to 70°C with an optimum at 55°C. The deoxyribonucleic acid base composition was 49.2 mol% guanine plus cytosine. Though this isolate conforms to Methanobacterium thermoformicium, its proper assignment awaits further studies. It has been deposited in the Deutsche Sammlung von Mikroorganismen as strain DSM 3012.

Purification, characterization and amino terminal sequence of the superoxide dismutase from Babesia hylomysci

Babesia hylomysci was found to contain two superoxide dismutase (SOD) isoenzymes with isoelectric points (pI) of 4.9 and 5.2. The two isoenzymes (45 and 47 kDa) were composed of two subunits of 22 kDa. An unique amino terminal sequence was determined up to 34 residues from the pooled isoenzymes and was identified as a sequence of SOD. The comparison of this N-terminal sequence of B. hylomysci SOD with 29 known Fe- or Mn-SODs showed more homologies with Fe-SODs.