Exploration des communautés bactériennes dans les systèmes aquaponiques

Aquaponics is a production system based on the dynamic equilibrium between fish, plants, and microorganisms. In order to better understand the role of microorganisms in this tripartite relationship, we studied the bacterial communities hosted in eight aquaponic and aquaculture systems. The bacterial communities were analyzed by 16S rRNA gene deep sequencing. At the phylum level, the bacterial communities from all systems were relatively similar with a predominance of Proteobacteria and Bacteroidetes. At the genus level, however, the communities present in the sampled systems were more heterogeneous. The biofilter samples harbored more diverse communities than the corresponding sump samples. The core microbiomes from the coupled and decoupled systems shared more common operational taxonomic units than with the aquaculture systems. Eventually, some of the taxa identified in the systems could have beneficial functions for plant growth and health, but a deeper analysis would be required to identify the precise functions involved in aquaponics

Polarization effects in autoionization processes - the 5d5g states in Barium

Accurate measurements of the autoionization widths of 5d5g levels of barium coupled to theoretical calculations, based on the eigenchannel R-matrix method and the multichannel quantum-defect theory, permit an investigation of the quadrupolar autoionization mechanism. The direct polarization of the inner electron by the outer one is an important correction to the Coulomb repulsion that causes autoionization. Also, the dielectronic polarization interaction significantly influences the autoionization widths. The occurrence of these polarization effects in the 5d5g doubly excited states with nonoverlapping valence electrons results in a significant narrowing of their widths and explains the failure of the ''single-configuration model'' for high-l Rydberg levels. © 1995 The American Physical Society