title: Degradation of cyanobacterial biomass in anoxic tidal-flat sediments: a microcosm study of metabolic processes and community changes.
abstract: To follow the anaerobic degradation of organic matter in tidal-flat sediments, a stimulation experiment with (13)C-labeled Spirulina biomass (130 mg per 21 g sediment slurry) was conducted over a period of 24 days. A combination of microcalorimetry to record process kinetics, chemical analyses of fermentation products and RNA-based stable-isotope probing (SIP) to follow community changes was applied. Different degradation phases could be identified by microcalorimetry: Within 2 days, heat output reached its maximum (55 μW), while primary fermentation products were formed (in μmol) as follows: acetate 440, ethanol 195, butyrate 128, propionate 112, H(2) 127 and smaller amounts of valerate, propanol and butanol. Sulfate was depleted within 7 days. Thereafter, methanogenesis was observed and secondary fermentation proceeded. H(2) and alcohols disappeared completely, whereas fatty acids decreased in concentration. Three main degraders were identified by RNA-based SIP and denaturant gradient gel electrophoresis. After 12 h, two phylotypes clearly enriched in (13)C: (i) Psychrilyobacter atlanticus, a fermenter known to produce hydrogen and acetate and (ii) bacteria distantly related to Propionigenium. A Cytophaga-related bacterium was highly abundant after day 3. Sulfate reduction appeared to be performed by incompletely oxidizing species, as only sulfate-reducing bacteria related to Desulfovibrio were labeled as long as sulfate was available.
authors.affiliation: Institut für Chemie und Biologie des Meeres, Carl-von-Ossietzky Universität Oldenburg, Niedersachsen, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Graue
authors.forename: Bert
authors.initials: B
authors.lastname: Engelen
authors.forename: Heribert
authors.initials: H
authors.lastname: Cypionka
mesh_terms: D000693:Anaerobiosis; D018533:Biomass; D002151:Calorimetry; D000458:Cyanobacteria / Q000254:growth & development / Q000378:metabolism*; D058645:Denaturing Gradient Gel Electrophoresis; D003901:Desulfovibrio / Q000254:growth & development / Q000378:metabolism; D005285:Fermentation; D019015:Geologic Sediments / Q000382:microbiology*; D012329:RNA, Bacterial / Q000032:analysis; D012623:Seawater / Q000382:microbiology; D053545:Spirulina / Q000254:growth & development / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism*
chemical_list: D012329:RNA, Bacterial; D013431:Sulfates