Biodégradation du Penta- et 2,4,6-tri-chlorophenol durant la digestion anaérobie des déchets non dangereux

International audienceIn this study isotopic tracing using C-13 labelled pentachlorophenol (PCP) and 2,4,6-trichlorophenol (2,4,6-TCP) is proposed as a tool to distinguish the loss of PCP and 2,4,6-TCP due to biodegradation from other physical processes. This isotopic approach was applied to accurately assess in situ PCP and 2,4,6-TCP degradation under methanogenic conditions in several microcosms made up of household waste. These microcosms were incubated in anaerobic conditions at 35 degrees C (mesophilic) and 55 degrees C (thermophilic) without agitation. The volume of biogas produced (CH4 and CO2), was followed for a period of 130 days. At this stage of stable methanogenesis, C-13(6)-PCP and C-13(6)-2,4,6-TCP were introduced anaerobically in microcosms and its monitoring at mesophilic and thermophilic conditions was performed in parallel by gas chromatography mass spectrometry (GC-MS) and gas chromatography isotope-ratio mass spectrometry (GC-IRMS). This study proved the almost total dechlorination of bioavailable PCP and 2,4,6-TCP into 4-CP at 35 degrees C. Nevertheless, high rate adsorption in particular materials of the two compounds was observed. Furthermore, Carbon-13 Nuclear Magnetic Resonance (C-13-NMR) Spectroscopy analysis of C-13 labelled 2,4,6-TCP mesophilic incubations showed the partial mineralization of 4-CP at 35 degrees C to acetate and then to HCO3-. Consequently, NMR results confirm the biogas isotopic results indicating the mineralization of C-13 labelled 2,4,6-TCP into C-13 (CH4 and CO2). Concerning C-13 labelled PCP mesophilic incubations, the isotopic composition of the biogas still natural until the day 262. In contrast, no de chlorination was observed at 55 degrees C. Thus PCP and 2,4,6-TCP were persistent in thermophilic conditions

Detection of WWE2-related Lentisphaerae by 16S rRNA gene sequencing and fluorescence in situ hybridization in landfill leachate

International audienceWe collected samples of anaerobic landfill leachate from municipal solid waste landfill (Vert-le-Grand, France) and constructed 16S rRNA clone libraries using primers targeting Planctomycetes and relatives (Pla46F and 1390R). Analyses of 16S rRNA gene sequences resulted in the abundant representation of WWE2-related Lentisphaerae, members of the phylum Lentisphaerae, in the clone library (98% of the retrieved sequences). Although the sequences that are phylogenetically affiliated with the cultured isolate Victivallis vadensis were identified (WWE2 subgroup II), the majority of the sequences were affiliated with an uncultured Lentisphaerae lineage (WWE2 subgroup I). We designed oligonucleotides probes targeting the specific 16S rRNA gene regions of those 2 subgroups. Fluorescence in situ hybridization confirmed the abundance of the uncultivated WWE2 subgroup I in our leachate samples.Nous avons récolté des échantillons anaérobies du lixiviat d'une décharge municipale de déchets solides (Vert-le-Grand, France), et nous avons construit des banques de clones d'ARNr 16S à l'aide d'amorces ciblant Planctomycetes et les bactéries apparentées (Pla46F et 1390R). Les analyses des séquences géniques de l'ARNr 16S ont révélé que les séquences du groupe WWE2 relié aux Lentisphaerae, appartenant au phylum Lentisphaerae étaient abondamment représentées dans la banque de clones (98 % des séquences retrouvées). Même si des séquences affiliées d'un point de vue phylogénique à l'isolat cultivé Victivallis ont été identifiées (sous-groupe II de WWE2), la majorité des séquences étaient affiliées à un lignage non cultivé de Lentisphaerae (sous groupe I de WWE2). Nous avons conçu des sondes d'oligonucléotides qui ciblaient des régions spécifiques du gène de l'ARNr 16S de ces 2 sous-groupes. L'hybridation in situ fluorescente a confirmé l'abondance du sous-groupe I de WWE2 non cultivé dans les échantillons de lixiviat

Members of the uncultured bacterial candidate division WWE1 are implicated in anaerobic digestion of cellulose

International audienceClones of the WWE1 (Waste Water of Evry 1) candidate division were retrieved during the exploration of the bacterial diversity of an anaerobic mesophilic (35 +/- 0.5 degrees C) digester. In order to investigate the metabolic function of WWE1 members, a 16S rRNA gene -based stable isotope probing (SIP) method was used. Eighty-seven percent of 16S r rRNA gene sequences affiliated to WWE1 candidate division were retrieved in a clone library obtained after polymerase chain reaction (PCR) amplification of enriched DNA fraction from anaerobic municipal solid waste samples incubated with C-13-cellulose, at the end of the incubation (day 63) using a Pla46F-1390R primer pair. The design of a specific WWE1 probe associated with the fluorescence in situ hybridization (FISH) technique corroborated the abundant representation of WWE1 members in our C-13-cellulose incubations. Secondary ion mass spectrometry-in situ hybridization (SIMSISH) using an iodine-labeled oligonucleotide probe combined with high-resolution nanometer-scale SIMS (NanoSIMS) observation confirmed the isotopic enrichment of members of WWE1 candidate division. The C-13 apparent isotopic composition of hybridized WWE1 cells reached the value of about 40% early during the cellulose degradation process, suggesting that these bacteria play a role either in an extracellular cellulose hydrolysis process and/or in the uptake fermentation products