51. Distribution of sulfate-reducing and methanogenic bacteria in anaerobic aggregates determined by microsensor and molecular analyses
- Author
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Piet N.L. Lens, Jakob Zopfi, Cecilia M. Santegoeds, Lars Riis Damgaard, Gerard Muyzer, Dirk de Beer, and Gijs Hesselink
- Subjects
animal structures ,Electron donor ,Biosensing Techniques ,Sulfides ,Biology ,Applied Microbiology and Biotechnology ,Microbiology ,Bacteria, Anaerobic ,chemistry.chemical_compound ,GRADIENT GEL-ELECTROPHORESIS ,Bioreactor ,Life Science ,Sulfate ,Sulfate-reducing bacteria ,In Situ Hybridization, Fluorescence ,Phylogeny ,chemistry.chemical_classification ,WIMEK ,Ecology ,Sulfates ,16S RIBOSOMAL-RNA ,GRANULAR SLUDGE ,MICROSCALE BIOSENSOR ,General Microbial Ecology ,IN-SITU HYBRIDIZATION ,Biodegradation ,biology.organism_classification ,Anaerobic digestion ,chemistry ,Propionate ,SP-NOV ,Environmental Technology ,Milieutechnologie ,PROPIONATE-OXIDIZING BACTERIA ,DESULFORHABDUS-AMNIGENUS ,SULFIDE OXIDATION ,Methane ,Bacteria ,FJORD MARIAGER FJORD ,Food Science ,Biotechnology ,Nuclear chemistry - Abstract
Using molecular techniques and microsensors for H 2 S and CH 4 , we studied the population structure of and the activity distribution in anaerobic aggregates. The aggregates originated from three different types of reactors: a methanogenic reactor, a methanogenic-sulfidogenic reactor, and a sulfidogenic reactor. Microsensor measurements in methanogenic-sulfidogenic aggregates revealed that the activity of sulfate-reducing bacteria (2 to 3 mmol of S 2− m −3 s −1 or 2 × 10 −9 mmol s −1 per aggregate) was located in a surface layer of 50 to 100 μm thick. The sulfidogenic aggregates contained a wider sulfate-reducing zone (the first 200 to 300 μm from the aggregate surface) with a higher activity (1 to 6 mmol of S 2− m −3 s −1 or 7 × 10 −9 mol s −1 per aggregate). The methanogenic aggregates did not show significant sulfate-reducing activity. Methanogenic activity in the methanogenic-sulfidogenic aggregates (1 to 2 mmol of CH 4 m −3 s −1 or 10 −9 mmol s −1 per aggregate) and the methanogenic aggregates (2 to 4 mmol of CH 4 m −3 s −1 or 5 × 10 −9 mmol s −1 per aggregate) was located more inward, starting at ca. 100 μm from the aggregate surface. The methanogenic activity was not affected by 10 mM sulfate during a 1-day incubation. The sulfidogenic and methanogenic activities were independent of the type of electron donor (acetate, propionate, ethanol, or H 2 ), but the substrates were metabolized in different zones. The localization of the populations corresponded to the microsensor data. A distinct layered structure was found in the methanogenic-sulfidogenic aggregates, with sulfate-reducing bacteria in the outer 50 to 100 μm, methanogens in the inner part, and Eubacteria spp. (partly syntrophic bacteria) filling the gap between sulfate-reducing and methanogenic bacteria. In methanogenic aggregates, few sulfate-reducing bacteria were detected, while methanogens were found in the core. In the sulfidogenic aggregates, sulfate-reducing bacteria were present in the outer 300 μm, and methanogens were distributed over the inner part in clusters with syntrophic bacteria.