title: Methane microprofiles in a sewage biofilm determined with a microscale biosensor.
abstract: Microprofiles of the methane concentration in a 3.5-mm-thick sewage outlet biofilm were measured at high spatial and temporal resolution using a microscale biosensor for methane. In the freshly collected biofilm, methane was building up to a concentration of 175 mumol l-1 at 3 mm depth with a total methanogenesis of 0.14 mumol m-2 s-1, as compared to an aerobic respiration (including methane oxidation) of 0.80 mumol m-2 s-1. A model biofilm was established by homogenisation of an in situ biofilm and 12 days of incubation with surplus sodium acetate. The homogenised biofilm was able to maintain 50% of the methanogenic activity in the absence of external electron donor. Oxygen had only a minor effect on the methane production, but aerobic respiration consumed a substantial part of the produced methane and was thus an important control on methane export from the biofilm. A concentration of 2 mmol l-1 nitrate was shown to inhibit methanogenesis only in the upper layer of the biofilm, whereas a further addition of 2 mmol l-1 sulphate inhibited methanogenesis in the entire biofilm. The study demonstrated the power of the methane microsensor in the study of microhabitats with concurrent production and consumption of methane.
authors.affiliation: Department of Microbial Ecology, University of Aarhus, B.540 Ny Munkegade, DK-8000 Aarhus C, Denmark. lars.damgaard@biology.au.dk
authors.forename: L R
authors.initials: LR
authors.lastname: Damgaard
authors.forename: L P
authors.initials: LP
authors.lastname: Nielsen
authors.forename: N P
authors.initials: NP
authors.lastname: Revsbech
mesh_terms: D001419:Bacteria / Q000378:metabolism; D018441:Biofilms; D015374:Biosensing Techniques; D002138:Calibration; D004058:Diffusion; D008697:Methane / Q000032:analysis*; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology
chemical_list: D012722:Sewage; D008697:Methane