This contribution describes a method to minimize biofouling of ultrafiltration membranes by coating the membrane surfaces with a new type of zwitterionic polymer. Poly(2-((2-hydroxy-3-(methacryloyloxy) propyl) dimethylammonio) acetate) (poly(CBOH)) was grafted from polyethersulfone (PES) membranes by UV-photopolymerization. Bacteria deposition studies showed that the poly(CBOH) chemistry performed better than other common anti-fouling chemistries. Biofilm studies showed that poly(CBOH) functionalized PES membranes accumulated half the biovolume as unmodified membranes. A unique feature of this new polymer coating is that it can switch reversibly between the anti-fouling, zwitterion mode and an anti-microbial, quaternary amine mode. Switching pH and time needed for complete switching to occur were evaluated using poly(CBOH) functionalized silicon wafers. Switching pH was determined to be 1.0, with 15 min being required to switch between the zwitterion and quaternary amine chemistries. Biofilm mortality was elevated once the anti-fouling poly(CBOH) zwitterion was switched to the anti-microbial, poly(CB-Ring) quaternary amine, with dead-to-live cell ratio increasing from 0.33 to 1.04.