PubMed · 17033661
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Takashi Mino, Hiroyasu Satoh. 2006. Wastewater genomics.. https://doi.org/10.1038/nbt1006-1229
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The genetic structures of bacterial communities associated with Medicago truncatula Gaertn. cv. Jemalong line J5 (Myc+ Nod+) and its symbiosis-defective mutants TRV48 (Myc+ Nod-) and TRV25 (Myc- Nod-) were compared. Plants were cultivated in a fertile soil (Châteaurenard, France) and in soil from the Mediterranean basin showing a low fertility (Mas d'Imbert, France). Plant growth, root architecture, and the efficiency of root symbiosis of the three plant genotypes were characterized in the two soils. Structures of the bacterial communities were assessed by automated-ribosomal intergenic spacer analysis (A-RISA) fingerprinting from DNA extracted from the rhizosphere soil and root tissues. As expected, the TRV25 mutant did not develop endomycorrhizal symbiosis in any of the soils, whereas mycorrhization of line J5 and the TRV48 mutant occurred in both soils but at a higher intensity in the Mas d'Imbert (low fertility) than in the Châteaurenard soil. However, modifications of plant growth and root architecture, between mycorrhizal (J5 and TRV48) and nonmycorrhizal (TRV25) plants, were recorded only when cultivated in the Mas d'Imbert soil. Similarly, the genetic structures of bacterial communities associated with mycorrhizal and nonmycorrhizal plants differed significantly in the Mas d'Imbert soil but not in the Châteaurenard soil. Multivariate analysis of the patterns allowed the identification of molecular markers, explaining these differences, and markers were further sequenced. Molecular marker analysis allowed the delineation of 211 operational taxonomic units. Some of those belonging to the Comamonadaceae and Oxalobacteraceae (beta-Proteobacteria) families were found to be significantly more represented within bacterial communities associated with the J5 line and the TRV48 mutant than within those associated with the TRV25 mutant, indicating that these bacterial genera were preferentially associated with mycorrhizal roots in the Mas d'Imbert soil.
The carbon disulfide (CS2)-oxidizing bacterium Thiomonas sp. WZW was enriched and isolated using activated sewage sludge as inoculum. Growth of Thiomonas sp. WZW was observed on CS2, thiosulfate, dimethylsulfide (DMS), dimethyldisulfide (DMDS), and H2S. No growth occurred on dimethylsulfoxide, methanol, acetate, and on complex media with glucose, yeast extract, or tryptone. DMDS-grown cells respired CS2, DMS, and DMDS, while thiosulfate-grown cells did not respire CS2. Chemostat cultures growing on thiosulfate could be rapidly adapted to growth on CS2. Growth was observed between pH 6 and 8. The Ks values for CS2, thiosulfate, and sulfide of CS2-grown cells were between 5 and 10 microM. CS2 was inhibitory above 0.3 mM. A lab-scale biotrickling filter with lava stone as carrier material for treatment of CS2-polluted air was inoculated with Thiomonas sp. WZW. A rapid start up (95% removal in 1 week) was obtained at an inlet CS2 concentration of 2 cmol l(-1) and an initial space velocity (SV) of 54 h(-1). Subsequent thiosulfate addition for a week during start up increased the removal to 99%. The step-wise increase of SV to 130 h(-1) and a CS2 concentration to 3 micromol l(-1) resulted in a stable performance with a removal efficiency of 95%. Feeding mixtures of volatile sulfur compounds showed simultaneous conversion of H2S, CS2, dimethyldisulfide (DMDS), and DMS, with a preference in this order.
The ability of different molar-mass fractions of interstitial dissolved organic carbon (DOC) from a small stream to stimulate bacterial growth was determined. Growth was the greatest in the low-molar mass (<1 kDa) (LMM) fraction and the least in the high-molar mass (>10 kDa) (HMM) one. The LMM fraction consistently had a higher ratio of carbon to organic nitrogen than other fractions. The fluorescence in situ hybridization analysis revealed that bacterial populations in interstitial water were dominated by beta-Proteobacteria. gamma-Proteobacteria together with the Cytophaga-Flavobacteria cluster dominated in LMM DOC (66.3%) while the proportions of bacterial groups in HMM and medium-molar mass (MMM) fractions were more equal. The fact that gamma-Proteobacteria strongly dominates in LMM DOC fraction refutes the idea that LMM DOC is readily utilized by all heterotrophic bacteria.