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Spungin, D.

Publications and source records attributed to Spungin, D..

2 recordsLinked to original sources

Trichodesmium Erythraeum produces a higher photocurrent than other cyanobacterial species in bio-photo electrochemical cells.

In recent years, the increase in world energy consumption, and the worries from potential future disasters that may derive from climate change have inspired the motivation to develop renewable energy technologies. One of the promising methods is the utilization of whole bacterial cells to produce photocurrent in a bio-photo electrochemical cell (BPEC). The photocurrent derives from the photosynthesis pathway, while the redox couple NADP+/NADPH perform cyclic electron mediation between photosystem I inside the cells, and the anode. Over the years, various cyanobacterial species were utilized in diverse BPECs setups, while the photocurrent was enhanced by the addition of natural electron mediators such as NAD+, NADP+, Cytochrome C, Vitamin B1, and the artificial mediator potassium ferricyanide. The cyanobacterium Trichodesmium Erythraeum (Te) is a marine species that consist of high content of Phycocyanin and Phycoerythrin pigments that play a major role in photosynthesis enhancement. In this work, we produce for the first-time photocurrent from Te. We apply 2D-fluorescence measurements to detect its NADPH secretion and show that its photocurrent production is enhanced as a function of increasing electrolyte salinity. Finally, we produce photocurrent from additional cyanobacterial species: Synechocystis sp. PCC6803, Synechococcus elongatus PCC 7942, Acaryochloris marina MBIC 11017, and Spirulina, using their cultivation medium as electrolytes in the BPEC. We show that TE produces a photocurrent intensity that is significantly greater than all other species with and without the addition of exogenous electron mediators. The utilization of TE may pave the way toward the establishment of marine clean energy technologies.

microbiology↗

Massive export of diazotrophs across the tropical south Pacific Ocean

Diazotrophs are widespread microorganisms that alleviate nitrogen limitation in 60% of our oceans, regulating marine productivity. Yet, their contribution to organic matter export has not been quantified, making an assessment of their impact on the biological carbon pump impossible. Here, we demonstrate that cyanobacterial and non-cyanobacterial diazotrophs are massively exported down to 1000 m-depth in the western subtropical South Pacific Ocean (WTSP), accounting for up to 52-100% of the total particulate nitrogen export fluxes. We further demonstrate that small size unicellular diazotrophs (UCYN, 1-8 {micro}m) are exported more efficiently than filamentous diazotrophs (>100-1000 {micro}m) under the form of large (>50 {micro}m) aggregates linked by an extracellular organic matrix. Beyond the WTSP, our data are supported by analysis of the Tara Oceans metagenomes collected in other ocean basins, showing that diazotrophs are systematically detected in mesopelagic waters when present at the surface. We thus conclude that diazotrophs are key players in carbon sequestration in the ocean and need to be considered in future studies to improve the accuracy of current regional and global estimates of export.

microbiology↗