The adhesion of Escherichia coli, Pseudomonas putida and Acinetobacter calcoaceticus cells to Microdyn-Nadir ultrafiltration membranes of various chemical nature: PS100 (polysulfone), P005 (polyethersulfone), C 100 (regenerated cellulose) was studied. It was shown that an adhesiveness of the! microorganisms to the membranes essentially depends on hydrophobic/hydrophilic properties of both the cells and membranes. In particular, it was found that the adhesion of relatively hydrophilic E. coli to membrane surfaces is essentially lower comparing with the adhesion of more hydrophobic P. putida, or A. calcoaceticus cells. In a turn the microorganisms attachment to more hydrophobic polyethersulfone and polysulfone membranes is higher than to hydrophilic cellulose one. It was shown that the volume fluxes of membranes with adhesive microorganisms dropped while samples were kept in contact with natural surface water due to increasing of cell number on membrane surface. In attempts to reduce membrane biofouling, TiO2 particles were deposited on membrane surface with following ultraviolet (UV) irradiation at 365 nm. It was shown that due to photobactericidal effect the fluxes of surface modified membranes were 1.7-2.3 times higher comparing with those for control membrane samples (without TiO2 deposition and UV treatment).