Fig. 4

A Detection of GH92_b with FORM-GH92_b gene probe set in pure culture of Polaribacter Hel1_33_49 targeted with general bacterial 16 S rRNA probe EUB338I-III. B Detection of GH92_b with FORM-GH92_b gene probe set in Polaribacter spp. of “cluster 1a” (targeted with 16S rRNA probe POL405) in plankton samples taken in the German Bight on the 26th April 2012 and 3rd May 2012. Significance levels are indicated by asterisks (***: p ≤ 0.001, **: p ≤ 0.01), ns = not significant. Arrows in magenta show the detected gene signals, white arrows display gene-like signals in other non-target organisms, arrows in cyan point to cells that have a low ribosomal content. Micrographs display experiments marked with a cross in the bar plots. Shown micrographs are maximum intensity projections of processed images achieved with Airyscan microscopy in super-resolution mode. DNA was counterstained with DAPI (appears blue in ‘all channels’). RGA = relative gene abundance, NC = negative control, scale bar: 1 μm, error bars represent the standard deviations.