Figure 3.

Biofilm formation of P. larvae ERIC I (ATCC9545) and P. larvae ERIC II (DSM25430) cultivated in static liquid. Bacterial suspensions of P. larvae ERIC I (ATCC9545; A,D,G) and P. larvae ERIC II (DSM25430; B,E,H) in brain heart infusion (BHI) broth were incubated without agitation in six-well-plates at 37 °C for five (A,B) and six (D,E) days, or in 96-well-plates for six days (G,H). For each P. larvae genotype, three biological replicates were performed both for obtaining pictures under unstained conditions (A,B), after Congo red staining of the extracellular matrix (D,E), and Crystal violet staining of the bacterial cells adherent to the well walls (G,H). Negative controls for each assay are shown in (C,F, and I). Representative pictures are shown.