Henri-Charles Dubourguier

Initial steps of catabolism of trihydroxybenzenes in Pelobacter acidigallici

The initial steps of the anaerobic degradation of trihydroxylated aromatic monomers were investigated in a strain (AG2) isolated on gallic acid and identified as Pelobacter acidigallici. Kinetic studies showed that strain AG2 fermented gallic acid into acetate with a transient accumulation of pyrogallol and phloroglucinol in the medium. In addition phloroglucinol was produced from all other trihydroxylated aromatic monomers and pyrogallol from 2,3,4-trihydroxybenzoate. Although protocatechuate did not support growth of the organism, it was partially decarboxylated by resting cells of strain AG2. Cell free extract of strain AG2 catalysed the oxidation of NADPH in presence of resorcinol, 2,4,6-trihydroxybenzoate and phloroglucinol. However, comparison of activities indicated that the latter was the true physiological electron acceptor. Phloroglucinol and its reduction product dihydrophloroglucinol appeared thus to play a key role in metabolism of trihydroxybenzenes and a unified pathway, involving a decarboxylation of trihydroxybenzoates, a para transhydroxylation of pyrogallol into phloroglucinol and the formation of dihydrophloroglucinol, was proposed.

Characterization of two strains of Pelobacter carbinolicus isolated from anaerobic digesters

In anaerobic industrial digesters treating wastewaters from food industry, the sludges showed high capacities to degrade ethanol. The main syntrophic ethanoldegrading organisms were characterized as Pelobacter carbinolicus. During acetoin degradation, butanediol isomers were shown to be transiently produced. In coculture with Methanobrevibacter arboriphilus, the strains oxidized not only primary monoalcohols but also 1,2- and 1,3-diols. Ecological importance as well as metabolic pathways of diol degradation are discussed.

Purification of component C from Methanosarcina mazei and immunolocalization in Methanosarcinaceae

Studies on immunological relationships among Methanosarcina genus using immunofluorescence and immunoprecipitation showed that a common antigen can be extracted by shaking in aqueous phase. This antigen was purified from Methanosarcina mazei. The protein had a molecular weight of 283400 daltons with three subunits, α=68000, β=43200 and γ=30500. It contained nickel, coenzyme M and F430. Its biochemical characteristics identified this antigen as the component C of the methyl CoM reductase complex. But EPR study showed that the nickel was Ni(II). Biological activity was detectable neither by heterologous in vitro assay nor by the DTT assay. Immunogold labelling showed that the component C was located randomly in the cytoplasm in Methanosarcina species and in Methanothrix soehngenii. In addition, specific labelling was also observed outside of the heteropolysaccharidic envelopes probably due to the absorption of component C released by the lysis of some cells in the clumps.

Light and electronic microscopic studies of the changes in the intestinal mucosa of gnotobiotic calves infected with a wild rotavirus

Summary Experimental infection of four gnotobiotic calves by a rotavirus isolated from the faeces of diarrheic calves caused non-fatal diarrhoea without dehydration. Lesions of the alimentary mucosa appear well before the onset of diarrhoea and are characterized by a release of mucus in the anterior part of the intestine. By the time diarrhoea begin, different types of rotavirus particules are present in the enterocytes of the mucosa, and mucus contents of distal intestine are affected. At this stage of the disease, the virus causes epithelial cells in the small intestine to desquamate and changes the secretion of mucus in the small as well as the large intestine. The very intense virus multiplication is completed within 18 h. Intracellular rotavirus disappear very quickly after the onset of diarrhoea, and cannot be detected even during the acute phase of the disease. Regeneration of the mucosa takes place slowly, and the cellular and structural lesions are still visible more than 4 days after the diarrhoea stopped.

Ultrastructural and Biochemical Studies of the Cell Sheath of Methanothrix soehngenii

Glycoproteins are present in the cell envelopes of some Eubacteria (Kupcu et al. 1984) and Archaebacteria (Mescher and Strominger 1976, Wieland et al. 1980). Among Archaebacteria, the methanogens exhibit various types of cell envelopes (Kandier and Konig 1985), some of them being protein surface-layers associated with carbohydrates. Methanothrix soehngenii OPF (Zehnder et al. 1980) and M. concilii GP6 (Patel 1984) present similar characteristics and have been recently proposed as a synonym (Touzel et al. 1988).