Fig. 4

Representative ESEM images of structures formed by P. mirabilis on chitin between 24 and 96 h. Crystalline-like depositions observed at 24 h on the clinical strain as type 1 (*) and type 2 (arrow) crystals a, and on the environmental strain as saturated amorphous crystalline material b. Channels interspersed within biofilms of clinical c and environmental d strains at 48 h. Pillar formations present at 24 h and absent until 96 h in the clinical e and environmental f strains, respectively. Mushroom-like structures with channels embedded in the middle of the biofilm of clinical and environmental strains at 96 h g and h, respectively. Head arrows indicate the structures in each case of study