Hur vidmakthålls nedbrytning av organiskt material över redox gradienter: samhällsförändringar eller anpassning?
Tidsperiod: 2013-01-01 till 2015-12-31
Projektledare: Stefan Bertilsson
Budget: 3 245 000 SEK
Bacteria in lakes hold central roles in degradation of organic matter. This process takes place both under oxic and anoxic conditions, but little is known about the identity, metabolism and environmental constraints of the heterotrophic organisms doing the job. In the current project we will test the hypothesis that an abundant subset of bacterioplankton communities in lakes are able to degrade organic substrates and grow under both oxic and anoxic conditions. Such metabolic versatility would influence ecosystem-scale carbon cycling and we propose that it would confer a major selective advantage in lakes and other system where organic matter and heterotrophic degraders are exposed to rapid and reoccurring shifts in redox. Sinking particles of biogenic origin and the gradual anoxia developing in hypolimnia of seasonally stratified lakes will be used as models. We will determine to what extent heterotrophic bacteria from oxic surface waters sustain their ability to degrade organic matter even in the absence of oxygen and reveal the identities of this community subset. Metabolic and genomic adaptations to such shifts in electron acceptor availability will be uncovered and ecological implications discussed. Experiments will be performed to test if such electron-acceptor controlled changes in microbial community features will cause preferential oxidation of specific types of organic substrates and alter the partitioning of degraded organic matter into new biomass, CO2 and CH4.