title: Changes in the acetogenic population in a mesophilic anaerobic digester in response to increasing ammonia concentration.
abstract: Changes in the acetogenic population were investigated in an experimental laboratory-scale biogas reactor (37°C) subjected to gradually elevated ammonia levels (0.8 to 6.9 g NH(4)(+)-N L(-1)). A shift from aceticlastic acetate degradation to syntrophic acetate oxidation had previously been confirmed in this reactor. In a parallel control reactor, operating at constant ammonia levels (0.65-0.90 g NH(4)(+)-N L(-1)), acetate degradation proceeded via the aceticlastic pathway throughout the operating period (660 d). The acetogenic populations in the reactors were analysed using degenerated primers designed to target the functional gene encoding a key enzyme of the acetyl-CoA pathway, 10-formyltetrahydrofolate synthetase (FTHFS). The analysis consisted of terminal restriction fragment length polymorphism (T-RFLP) analysis coupled with the construction of clone libraries, and quantitative PCR (qPCR) analysis. The T-RFLP data obtained were statistically analysed by non-metric multidimensional scaling. The most abundant FTHFS genes recovered in the clone libraries were assigned to terminal restriction fragments of the T-RFLP profile. The results of the investigation clearly indicated that increased ammonia concentration substantially influenced the putative acetogenic population structure and caused two distinct shifts of the most abundant members; however, the identity of the dominating species remains unknown, as none of the genes had been identified previously. Despite the shifts in the population, the qPCR analysis revealed a relatively stable abundance of the acetogenic population throughout the operation.
authors.affiliation: Department of Microbiology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Uppsala, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Westerholm
authors.forename: Bettina
authors.initials: B
authors.lastname: Müller
authors.forename: Veronica
authors.initials: V
authors.lastname: Arthurson
authors.forename: Anna
authors.initials: A
authors.lastname: Schnürer
mesh_terms: D000085:Acetates / Q000378:metabolism*; D000641:Ammonia / Q000378:metabolism*; D000693:Anaerobiosis; D019149:Bioreactors / Q000382:microbiology*; D058448:Biota; D016000:Cluster Analysis; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013696:Temperature
chemical_list: D000085:Acetates; D003470:Culture Media; D004269:DNA, Bacterial; D000641:Ammonia