Purity of E. coli cells before and after separation from suspended mixtures and biofilms. Purity of E. coli cells before and after one- or two-step IMS from (A) suspended mixtures and (B) biofilms of E. coli and S. maltophilia cells. Suspended mixtures were prepared by mixing suspended E. coli cells (104-106 CFU/ml) with S. maltophilia cells (105-108 CFU/ml). Biofilms were scraped from a flow-cell system and dispersed into suspensions of single cells (E. coli 2.3 × 106 CFU/ml, S. maltophilia 2.6 × 107 CFU/ml). Two independent IMS experiments were performed for aliquots of dispersed biofilms. Error bars indicate standard deviations of two or three replicate plate counts.