Zwitterionic modification of membrane surfaces is a promising approach to decrease membrane biofouling. In this study, biofouling properties of two commercial polyamide (PA) reverse osmosis (RO) desalination membranes coated with zwitterionic sulfobetaine silane compounds including4-(diethyl(3-(trimethoxysilyl)propyl) ammonia)butane-l-sulfonate (EPBS) and 3-(dimethyl(3-(trimethoxysilyl)propypammonia)propane-1-sulfonate (MPPS) were investigated using five different marine bacteria isolated from Bosphorus, Turkey. To mimic the real environment, new marine strains were isolated for the biofouling assay. The biofouling behavior was monitored at different maturation stages of biofouling bacteria on the surfaces of the membranes. In addition, the permeability variation of the coated membranes was analyzed by measuring the flux values before and after the biofouling process compared to the uncoated, control membrane. According to the results, while commercial control RO membranes were highly prone to biofouling, zwitterionic sulfobetaine silane coated membranes showed a strong anti-bacterial effect against the isolated marine biofouling bacteria with significant bio-film adhesion resistance. When the flux value of commercial uncoated control membrane decreased by 38% after biofouling, the flux reduction was 16% and 20% in the EPBS and MPPS coated membranes, respectively.