Development of oxygen microsensors for monitoring cyanobacterial photosynthesis in Roman hypogea

Clark type oxygen microsensors were developed for measurement of photosynth etic light response in cyanobacteria isolated from epilithic microbial comm unities colonizing Roman hypogea. Microelectrodes were built using polyeste r or tenon insulated platinum wires as working electrodes and silver wires as reference electrodes, then inserted in glass capillaries previously coat ed at one end with a silicon gas-permeable membrane. Platinum was polarized at -750 mV vs Ag/AgCl, and 0.1 M KCI was used as supporting electrolyte. S tability, sensitivity and reproducibility of the probes were tested. These cost effective sensors exhibited comparable behaviour with those commercial ly available. Photosynthesis of selected cyanobacterial species was followe d by monitoring the oxygen evolution at increasing irradiances (P/I curves) .