Fig. 3

Detection of GH92 genes with direct-geneFISH in plankton samples taken during the spring bloom in the German Bight. A Relative cell abundances of Polaribacter spp. of “cluster 3a” targeted with the 16S rRNA probe POL183a and Formosa spp. targeted with the 16S rRNA probe FORM181B based on CARD-FISH counts [13]. Chlorophyll a concentration was taken as a proxy for algae biomass (gray area). Black arrows indicate dates from which samples were used for experiments (left: 20th April 2010, right: 26th April 2010). B Relative gene abundance (RGA), NC = negative control, error bars in histograms represent standard deviations of mean RGAs. Significance is indicated by asterisks (p ≤ 0.001). C Overview image to the magnified regions of interest to the right of Polaribacter spp. of “cluster 3a” targeted with the 16S rRNA probe POL183a and POL-GH92_a in a plankton sample. D Overview image to the magnified regions of interest to the right of Formosa spp. targeted with the 16S rRNA probe FORM181B and FORM-GH92_a and _b in a plankton sample. DNA was counterstained with DAPI (appears blue in ‘all channels’). Arrows in magenta and yellow show the respective gene signals and white arrows indicate gene-like signals in non-target organisms. Arrow in cyan points to a cell with a low ribosome content. All micrographs are maximum intensity projections of processed images achieved with Airyscan microscopy in super-resolution mode. Scale bar: 1 μm.