Confocal microscopy images of immunofluorescence staining for Bradyrhizobium sp. prepared from pure culture and plant nodules.

Immunofluorescence staining of various bacterial targets in both pure culture and nodule forms are shown. The bacteria tested include Bradyrhizobium sp. strains DOA9 (A), SUTN9-2 (B), SUTN1-12 (C), and USDA110 (D). The bacterial samples were stained with various antibodies, i.e., rabbit polyclonal antibody, two clones of phage-displayed rabbit scFv, i.e., RB9 and RG8, which contained identical DNA sequence. Phage-displayed scFv antibody clone 3C1 that bind aflatoxin B1 was used as a negative control. Green spots indicated the green fluorescent staining of phage display scFv or polyclonal antibody, using secondary antibody conjugated to FITC. Plant cell walls were stained with a blue fluorophore (Calcofluor white M2R) and emitted blue color. The bacteroid are shown as green spots inside a blue plant cavity. Scale bar is 10 μm at 80× magnification, and 100 μm at 10× magnification for pure culture and nodule samples, respectively.