Silica nanoparticles were synthesized and functionalized with different chemical groups (hydroxyl, mercapto, isocyanate, carboxyl and amino) in order to understand how different functional groups favor the interaction between nanoparticles and the envelope of different bacteria. Obtained results showed that bacteria-nanoparticle interation is driven by the nature of nanoparticles surface and that different types of bacteria envelope do not influence this mechanism.