Abstract: The invention relates to devices and methods for detecting a substance by cell surface polarizations and the detection thereof by means of PPR or particle-mediated fluorescence. The device for detecting a substance by cell surface polarization according to the invention has cells, wherein a gene the expression of which leads to the polarized presentation of a protein on the surface of the cell is placed under the control of a promotor which can be regulated by the substance to be detected, nanoparticles which are functionalized with a molecule which can bind specifically to the surface-exposed protein, and at least one optical measurement device, such that an accumulation of the nanoparticles on the surface of the cells can be detected by particle plasmon resonance or particle-mediated fluorescence.

Abstract: In a method for detection of microorganisms and/or their activity with biosensors, on a surface of a substrate over portions thereof at least one ligand for binding a receptor or at least one receptor for a ligand or at least one ligand for binding a receptor and at least one receptor for either the one or a further ligand are immobilized chemically, physically, or biologically, wherein physical or physicochemical changes, caused at receptors by binding of ligands that are emitted by microorganisms in the process of quorum sensing are measured.