Assessment of the microbial community in the cathode compartment of a plant microbial fuel cell

Introduction: In plant microbial fuel cells (plant-MFCs) living plants and microorganisms form an electrochemical unit able to produce clean and sustainable electricity from solar energy. It is reasonable to assume that besides the bacteria in the anode compartment also the cathode compartment plays a crucial role for a stable high current producing plant-MFC. In this study we aim to identify dominant bacterial species in the cathode compartment of the plant-MFC

Monophyletic group of unclassified γ-Proteobacteria dominates in mixed culture biofilm of high-performing oxygen reducing biocathode

International audienceSeveral mixed microbial communities have been reported to show robust bioelectrocatalysis of oxygen reduction over time at applicable operation conditions. However, clarification of electron transfer mechanism(s) and identification of essential micro-organisms have not been realised. Therefore, the objective of this study was to shape oxygen reducing biocathodes with different microbial communities by means of surface modification using the electrochemical reduction of two different diazonium salts in order to discuss the relation of microbial composition and performance. The resulting oxygen reducing mixed culture biocathodes had complex bacterial biofilms variable in size and shape as observed by confocal and electron microscopy. Sequence analysis of ribosomal 16S rDNA revealed a putative correlation between the abundance of certain microbiota and biocathode performance. The best performing biocathode developed on the unmodified graphite electrode and reached a high current density for oxygen reducing biocathodes at neutral pH (0.9A/m(2)). This correlated with the highest domination (60.7%) of a monophyletic group of unclassified γ-Proteobacteria. These results corroborate earlier reports by other groups, however, higher current densities and higher presence of these unclassified bacteria were observed in this work. Therefore, members of this group are likely key-players for highly performing oxygen reducing biocathodes.[on SciFinder (R)

NOTIFy (non-toxic lyophilized field)-FISH for the identification of biological agents by Fluorescence in situ Hybridization.

The rapid and reliable diagnostics of highly pathogenic bacteria under restricted field conditions poses one of the major challenges to medical biodefense, especially since false positive or false negative reports might have far-reaching consequences. Fluorescence in situ hybridization (FISH) has the potential to represent a powerful microscopy-based addition to the existing molecular-based diagnostic toolbox. In this study, we developed a set of FISH-probes for the fast, matrix independent and simultaneous detection of thirteen highly pathogenic bacteria in different environmental and clinical sample matrices. Furthermore, we substituted formamide, a routinely used chemical that is toxic and volatile, by non-toxic urea. This will facilitate the application of FISH under resource limited field laboratory conditions. We demonstrate that hybridizations performed with urea show the same specificity and comparable signal intensities for the FISH-probes used in this study. To further simplify the use of FISH in the field, we lyophilized the reagents needed for FISH. The signal intensities obtained with these lyophilized reagents are comparable to freshly prepared reagents even after storage for a month at room temperature. Finally, we show that by the use of non-toxic lyophilized field (NOTIFy)-FISH, specific detection of microorganisms with simple and easily transportable equipment is possible in the field