Identifying N2-fixing microorganisms in photosynthetic microbial mats by Stable Isotope Probing (SIP) and nanometer-scale Secondary Ion Mass Spectrometry (nanoSIMS)

• Antragstellerin: Dr. Dagmar Woebken
• Fachliche Zuordnung: Mikrobielle Ökologie und Angewandte Mikrobiologie
• Förderung: Förderung von 2010 bis 2011
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 164666922

Phototsynthetic microbial mats are important ecosystems in shallow-water marine environments since they supply these often nitrogen-limited environments with biologically available nitrogen, however the populations that fix nitrogen (diazotrophs) are poorly understood. Sequencing of the nifH genes and transcripts indicated that unicellular and filamentous cyanobacteria as well as heterotrophic bacteria could represent the dominant diazotrophs in microbial mats. However, the presence and/or transcription of this gene do not necessarily indicate that those organisms are primarily responsible for N2 fixation in this system due to transcriptional and posttranslational regulation. In the proposed research, the diazotrophic community of photosynthetic microbial mats will be studied using a combination of techniques. First, nifH gene and transcript sequencing will identify the potential diazotrophs and allows the design of primers and probes for the next task. Second, the abundance and seasonal succession of potential diazotrophs will be determined by nifH quantitative PCR and quantitative RT PCR. Third, this will be combined with 15N2 incubation experiments, in situ hybridization and investigations with nanometer-scale Secondary Ion Mass Spectrometry (nanoSIMS). In situ hybridization using halogen labeled tyramides and nanoSIMS (so called EL-FISH or HISH-SIMS) will assess the microbial community enriched in 15N, thereby allowing the identification of the microbial community that fixed N2 and the quantification of their metabolic activities at the single cell level.

• DFG-Verfahren: Forschungsstipendien
• Internationaler Bezug: USA
• Gastgeber: Professor Dr. Alfred Spormann