Interaction of nanoparticles with biomolecules and bioobjects is widely used in bioelectronics, for example, in biosensorics. In the work changes in optical properties (absorption spectra) on Ag nanoparticles with bacteria Bacillus clausii has been studied. Theoretically, it has been shown that adsorption of the nanoparticles on the bacteria leads to changes in the plasmonic properties of nanoparticles and should lead to changes in absorption spectra of these liquid bionanosystems in time. Experimentally it has been observed that indeed the intensity of the light absorption at the nanoparticles peak becomes less intensive in time. It has also been shown that in systems with Ag nanoparticles intensity of the light absorption at the bacteria peak is less than in an intact bacterial sample. These phenomena indicate the adsorption of nanoparticles on bacteria and suppression of bacterial growth by Ag nanoparticles.