Fig. 4: Evidence for H2 consumption by hydrogenotrophic denitrifiers in photogranules.
From: Interspecies hydrogen transfer between cyanobacteria and symbiotic bacteria drives nitrogen loss
a Gene expression of different electron acceptors in the granular sample (G, 2–5 mm, n = 3) and floc sample (F, <0.2 mm, n = 3) harvested on the last operational day. Heatmaps show the total normalized gene expression (in RPKM). The average RPKM of the two samples is individually shown in two columns. ** represent these two genes over 10× more highly expressed than the other electron acceptor genes. Nitrate (b) and nitrite (c) consumption profiles of photogranules under different concentrations of H2. d H2 consumption profile of photogranules under nitrate replicate and deprecate conditions. e CLSM image of photogranule cross-sections showing the spatial distribution of the two main families of hydrogenotrophic denitrifiers: f Burkholderaceae and (g) Rhodocyclaceae. Cyanobacteria shown by self-fluorescence of chlorophyll-a. Lines show the spatial distance of the target microbe to the surface of the CA. h The average three microprofiles of H2 (blue points) and NO3− (red points) in the same photogranule under dark conditions (left) when external NO3− and H2 are supplied. Consumption rates (right) of H2 and NO3− at each depth calculated from the microprofiles, assuming a spherical photogranule with a diameter of 3.2 mm. Source data are provided with this paper.
