Structure and function of benthic microbial community in highly variable freshwater systems

摘要: In the semi-arid Mediterranean regions, extended reaches of rivers and streams show a recurrent dry phases varying duration spatial extent. It is important to study effects water stress on riverine ecological processes since freshwater systems are crucial in linking terrestrial marine environments, My Doctorate thesis research, supported by European TempQsim project (EVK1-CT2002-00112), was aimed investigate dynamics microbial communities associated sediments temporary rivers. particular, I have been investigating structure function benthic bacterial their role carbon cycle characterized seasonal hydrologic regime. Bacterial abundance phylogenetic composition were assessed molecular techniques, while activity estimated measuring incorporation rates radioactive tracers immunofluorescence. From methodological point view, all applied techniques required specific optimization phase order increase analytical efficiency. detachment procedure extract purify cells from optimized combined use different chemical physical treatments, followed high-speed density gradient centrifugation using medium Nycodenz. This initially analyze with stable flow conditions (Rivers Albegna, Ente, Fiora – Tuscany, Italy; River Cremera Lazio, Italy). addition, efficiency situ hybridization (Fluorescence Situ Hybridization fluorescently monolabeled probes FISH; Fluorescence signal amplification Catalyzed Reporter Deposition CARD-FISH) tested regards physicochemical characteristics selected (i.e. sediment organic matter moisture content). this respect, CARD-FISH protocol improved better estimate occurrence clusters sediments. For field study, regularly collected at river outlet section Mulargia (Sardinia, A in-depth performed for analyses. Additional tests artificial microcosms experimentally describe responses drying rewetting processes, simulating desiccation re-inundation four (River Tagliamento - Krathis Greece; Pardiela Portugal). further laboratory experiment, community that primary colonized set up could contribute understand those microbes reside state low-activity promptly colonize new incoming end period. synthesis, my research contributed understanding functional The results help elucidate mechanisms involved transformation during drought periods, which attended length frequency as possible effect climatic changes.