Biotechnologie, Agronomie, Société et Environnement (Jan 2015)
Apport des analyses isotopiques et moléculaires pour la caractérisation des communautés fonctionnelles et des voies métaboliques au cours de la méthanogenèse dans des boues d'épuration
Abstract
Characterization of functional communities and metabolic pathways during methanogenesis in wastewater sludge by isotopic and molecular analysis. Description of the subject. Investigation of the relationships between methanogenic community and metabolic pathway dynamics during methanogenesis. Objectives. The objective was to use an isotopic approach coupled with molecular analysis to identify metabolisms and to understand the dynamics of Archaea under different temperature conditions. Method. Sludge was incubated anaerobically under mesophilic and thermophilic conditions. Biogas production was monitored, together with stable isotopic signatures of produced CH4 and CO2. Results. Isotopic signature values for CH4 indicated a change in methanogenic metabolism with time and temperature. CH4 was predominantly produced from H2/CO2 and acetoclastic metabolism at the beginning of the mesophilic incubations and after acetate injection. A progressive shift towards an acetoclastic metabolism was observed at the end of mesophilic incubations. This period was associated with stability within archaeal communities as monitored by automated ribosomal intergenic spacer analysis (ARISA) and FISH with oligonucleotidic probes targeting specifically the Archaea 16S rRNA gene. At the beginning of the thermophilic incubations and after acetate injection, methane was generated mostly from H2/CO2. At the end of the thermophilic incubations, an acetoclastic metabolism was observed and intergenic spacer analysis (ARISA) and FISH showed important shifts in archaeal communities. Conclusions. Isotopic methods coupled with molecular analyses enabled us to better understand methanogenesis and the involvement of archaeal populations, which varied according to temperature. We also observed a preadaptation of archaeal communities in thermophilic conditions, which could be due to the fact that mesophilic microorganisms were progressively eliminated during the thermophilic incubation period.
