Yeast cell metabolism investigated by CO2 production and soft X-ray irradiation

Results obtained using a new technique for studying cell metabolism are pre sented. The technique, consisting in CO2 production monitoring, has been ap plied to Saccharomyces cerevisiae yeast cells. Also the cells were irradiat ed using the soft X-ray laser-plasma source at Rutherford Appleton Laborato ry with the aim of producing a damage of metabolic processes at the wall le vel, responsible for fermentation, without great interference with respirat ion, taking place in mitochondria, and DNA activity. The source was calibra ted with PIN diodes and X-ray spectrometers and used Teflon stripes as targ et, emitting X-rays at about 0.9 keV, with a very low penetration in biolog ical material. X-ray doses delivered to the different cell compartments wer e calculated following a Lambert-Bouguet-Beer law. Immediately after irradi ation, the damage to metabolic activity was measured again by monitoring CO 2 production. Results showed a general reduction in gas production by irrad iated samples, together with non-linear and non-monotone response to dose. There was also evidence of oscillations in cell metabolic activity and of X -ray induced changes in oscillation frequency.