Resolution of Conflicting Signals at the Single-Cell Level in the Regulation of Cyanobacterial Photosynthesis and Nitrogen Fixation.

Unicellular, diazotrophic cyanobacteria temporally separate dinitrogen (N2) fixation and photosynthesis to prevent inactivation of the nitrogenase by oxygen. This temporal segregation is regulated by a circadian clock with oscillating activities of N2 fixation in the dark and photosynthesis in the light. On the population level, this separation is not always complete, since the two processes can overlap during transitions from dark to light.

Look@NanoSIMS--a tool for the analysis of nanoSIMS data in environmental microbiology.

We describe an open-source freeware programme for high throughput analysis of nanoSIMS (nanometre-scale secondary ion mass spectrometry) data. The programme implements basic data processing and analytical functions, including display and drift-corrected accumulation of scanned planes, interactive and semi-automated definition of regions of interest (ROIs), and export of the ROIs' elemental and isotopic composition in graphical and text-based formats. Additionally, the programme offers new functions that were custom-designed to address the needs of environmental microbiologists.

Detecting metabolic activities in single cells, with emphasis on nanoSIMS.

Investigating the contribution of microbial populations to biochemical processes of global significance is challenging as there are few approaches that can detect microbial metabolic activities on single-cell level. Given the widespread distribution and importance of microorganisms in elemental transformations, improved methods for measuring microbial activities in naturally occurring microbial communities is essential. In this article, microautoradiography (MAR), Raman microspectroscopy, and Secondary Ion Mass Spectrometry (SIMS) and their combination with isotope labeling and molecular genetic methods for cell identification (i.

Nitrogen fixation and transfer in open ocean diatom-cyanobacterial symbioses.

Many diatoms that inhabit low-nutrient waters of the open ocean live in close association with cyanobacteria. Some of these associations are believed to be mutualistic, where N(2)-fixing cyanobacterial symbionts provide N for the diatoms. Rates of N(2) fixation by symbiotic cyanobacteria and the N transfer to their diatom partners were measured using a high-resolution nanometer scale secondary ion mass spectrometry approach in natural populations.

Carbon and nitrogen fluxes associated with the cyanobacterium Aphanizomenon sp. in the Baltic Sea.

Carbon and nitrogen fluxes in Aphanizomenon sp. colonies in the Baltic Sea were measured using a combination of microsensors, stable isotopes, mass spectrometry, and nanoscale secondary ion mass spectrometry (nanoSIMS). Cell numbers varied between 956 and 33 000 in colonies ranging in volume between 1.