Nystatin-induced changes in yeast monitored by time-resolved automated single cell electrorotation

A widespread use of electrorotation for the determination of cellular and subcellular properties has been hindered so far by the need for manual recording of cell movements. Therefore a system has been developed that allows the automatic collection of electrorotation spectra of single cells in real time. It employs a hardware based registration of image moments from which object orientation is calculated. Since the camera's video signal is processed without intermediate image storage a high data throughput of about two recordings per second could be achieved independently of image resolution. This made it possible to monitor changes in cell membrane and cytoplasm of the yeast Saccharomyces cerevisiae under the influence of the antibiotic nystatin with a temporal resolution of 3 min. Up to 20 electrorotation spectra of an individual cell could be collected in the frequency range between 1 kHz and 1 GHz. Two distinct events 7 and 75 min after addition of nystatin were observed with a fast increase in membrane permeability accompanied by a nearly simultaneous drop in cytoplasmic conductivity.