Among nanomaterials, nanoparticule of inorganic metal oxide, such as titanium dioxide presents a great interest for scientific communities and industrial domain. The widespread use of titanium dioxide is due to its properties: high capacity of producing hydroxyl radicals, in an aqueous medium under UV irradiation; possibility to change the band gap with specific purpose to use the light in the visible range of the solar spectrum; chemically inert, even in extreme conditions; obtaining of this material using various methods, or availability at a relatively low cost. The aim of the study was to test the potential bactericidal/bacteriostatic effect of the titanium dioxide nanoparticles on some halophilic/halotolerant bacteria isolated from the mural paintings from Hurezi (Nesterenkonia sp., Halobacillus naozhouensis) and Humor (Halobacillus sp.) monasteries. These microorganisms are responsible for the rosy discolouration of mural paintings, as they are involved in the biodeterioration process. The antibacterial efficacy of titanium dioxide was evaluated by monitoring the bacterial growth (determination of the optical density at 660 nm) under dark and natural illumination conditions in laboratory, in the presence of different concentration of titanium dioxide. The biological activity was evaluated as dehydrogenase activity and was expressed as mg formazan %.