The application of the micro fluid segment technique for the investigation of highly resolved dose-response relationship at the physiological parameters segment-internal pH and growth of the cell culture is introduced. The method was used to study the concentration-dependent response of an Escherichia coli culture for the effectors 2,4-dinitrophenol (DNP) and an antibacterial peptide amide (KKVVFKVKFK-NH(2)). Large sequences with up to 250 micro fluid segments containing gradually varying concentrations of the effectors were generated using a PTFE micro fluidic arrangement, including a 7-port-manifold and PC-controlled syringe pumps. The response of the cell culture was characterized by a double sensor system allowing for simultaneous read out of metabolism-related changes as well as changes in cell density. A twin arrangement of a micro flow-through photometer and a micro flow-through fluorometer based on LED devices in connection with the application of pH-sensitive polymer sensor particles was applied. This experimental setup allows a detailed determination of drug-related changes in fluorescence intensity by the E. coli culture and the polymer particles as a function of time by tracking changes in pH and cell density. The application of the segmented flow technique for multi-parameter drug screenings provides new insights into the biological answer of bacteria cultures cultivated at the nanoliter scale. (c) 2009 Elsevier B.V. All rights reserved.