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

¹ Dipartimento di Fisica, Seconda Università di Milano Bicocca, via Emanueli 15, 20126 Milano, Italy
² INFM, Istituto Nazionale di Fisica della Materia, Milano, Italy
³ Dipartimento di Elettronica e Informazione, Politecnico di Milano, via Ponzio 34/5, 20133 Milano, Italy
⁴ Dipartimento di Scienza dei Materiali, Seconda Università di Milano Bicocca, via Emanueli 15, 20126 Milano, Italy
⁵ Rutherford Appleton Laboratory, Chilton Didcot, Oxon, OX11 OQX, UK

Received: 17 June 1998
Accepted: 24 September 1998
Published online: 15 January 1999

Abstract

Results obtained using a new technique for studying cell metabolism are presented. The technique, consisting in CO₂ production monitoring, has been applied to Saccharomyces cerevisiae yeast cells. Also the cells were irradiated using the soft X-ray laser-plasma source at Rutherford Appleton Laboratory with the aim of producing a damage of metabolic processes at the wall level, responsible for fermentation, without great interference with respiration, taking place in mitochondria, and DNA activity. The source was calibrated with PIN diodes and X-ray spectrometers and used Teflon stripes as target, emitting X-rays at about 0.9 keV, with a very low penetration in biological material. X-ray doses delivered to the different cell compartments were calculated following a Lambert-Bouguet-Beer law. Immediately after irradiation, the damage to metabolic activity was measured again by monitoring CO₂ production. Results showed a general reduction in gas production by irradiated 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.