A novel, mesophilic, strictly anaerobic, sulfate-reducing and propionate-oxidizing bacterium, strain Prop6T, was enriched and isolated from a municipal anaerobic sewage sludge digester. Cells were Gram-stain-negative, catalase-positive, oval rods, motile by means of amphitrichous flagella, non-spore-forming and contained menaquinone MK-5(H2) as the major respiratory quinone. The genomic DNA G+C content was 51.7 mol%. The optimal NaCl concentration, temperature and pH were 2-5 g l-1, 35 °C and pH 7.6, respectively. Strain Prop6T could only oxidize propionate, lactate and pyruvate (weakly) with sulfate, sulfite or thiosulfate, mainly to acetate. Strain Prop6T fermented pyruvate and lactate to acetate and propionate. The predominant cellular fatty acids were C14 : 0, C16 : 0, C16 : 1ω7, C16 : 1ω5, C17 : 1ω6 and C18 : 1ω7. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the newly isolated strain was a member of the genus Desulfobulbus, with Desulfobulbus elongatus DSM 2908T, Desulfobulbus propionicus DSM 2032T and Desulfobulbus rhabdoformis DSM 8777T as closest relatives among species with validly published names. On the basis of genotypic, phenotypic and chemotaxonomic characteristics, it is proposed that the isolate represents a novel species, Desulfobulbus oligotrophicus sp. nov. The type strain is Prop6T (=DSM 103420T=JCM 31535T).
Altering the gut microbiota can negatively affect human health. Efforts may be sustained to predict the intended or unintended effects of molecules not naturally produced or expected to be present within the organism on the gut microbiota. Here, culture-dependent and DNA-based approaches were combined to UHPLC-MS/MS analyses in order to investigate the reciprocal interactions between a constructed Human Gut Microbiota Model (HGMM) and molecules including antibiotics, drugs, and xenobiotics. Our HGMM was composed of strains from the five phyla commonly described in human gut microbiota and belonging to Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, and Actinobacteria. Relevantly, the bacterial diversity was conserved in our constructed human gut model through subcultures. Uneven richness distribution was revealed and the sensitivity of the HGMM was mainly affected by antibiotic exposure rather than by drugs or xenobiotics. Interestingly, the constructed model and the individual cultured strains respond with the same sensitivity to the different molecules. UHPLC-MS/MS analyses revealed the disappearance of some native molecules in the supernatants of the HGMM as well as in those of the individual strains. These results suggest that biotransformation of molecules occurred in the presence of our gut microbiota model and the coupled approaches performed on the individual cultures may emphasize new bacterial strains active in these metabolic processes. From this study, the new HGMM appears as a simple, fast, stable, and inexpensive model for screening the reciprocal interactions between the intestinal microbiota and molecules of interest.
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