Figure 2

Bacterial ingress in hydrogels over 18 hour. Confocal images and population profiles showing the ingress of Pseudomonas fluorescens (adhesin present) and Bacillus subtilis (without adhesin) into the PAA polymer, grafted PAA-mannan and freely absorbed PAA-mannan after 18 hours of incubation (all hydrogels were pre-swollen in nutrient solution). Here distinct differences between the presence or absence of mannan chains in the hydrogels and adhesin binding proteins on the cells are clearly seen. The xyz imaging dimensions were 211 µm × 211 µm × 200 µm respectively. Images represent the cross-section of CLSM scans, showing the biointerface (cells enter the 3D hydrogel from xy plane) and the inner bulk regions of bacteria-colonized polymer. Green indicates viable cells (SYTO 9 stained), while red indicates damaged cells (propidium iodide stained). The number of colonized P. fluorescens and the apparent movement of B. subtilis in the 3-D structure of hydrogels were quantified using ImageJ. Differences in microbial motility and colonization are shown in Suppl. Figure 3.