Pressure treatment has a differential effect on cyanide- and ethanol-induced autofluorescence response in yeast.

Abstract

Cellular processes associated with biological membranes and multimeric associations exhibit pressure sensitivity. In cellular respiration for example, pressure-regulated respiratory oxidases and cytochromes are found in piezophilic microbes, and pressure reduces oxygen consumption rates in eukaryotes. The presence of piezotolerant obligate aerobic yeasts in deep sea environments further justifies investigating pressure effects on cellular respiratory mechanisms. Ambient pressure analysis of UV-excited autofluorescence signals used for monitoring respiratory metabolism have identified multiple cellular NADH and NADPH conformations, significant because the distribution of conformational forms depends on metabolic conditions. Here, we use UV-excited autofluorescence spectroscopy with the spectral response quantified using phasor analysis to monitor cellular NADH and NADPH conformation in Saccharomyces cerevisiae (baker's yeast) suspensions after 30-minute pressure treatment at up to 11 kpsi (75.8 MPa). Specifically, we investigate the effects of pressure treatment on the autofluorescence response to the additions of cyanide and ethanol (both respiratory inhibitors at ambient pressure). The autofluorescence response to cyanide measured 30 min after pressure release shows a diminished response, while the response to ethanol shows no detectable difference when compared with the response prior to pressure treatment. Conditions for this study are similar to those previously reported to activate transcription factors in yeast due to pressure-induced stress tolerance, suggesting autofluorescence may be useful for assessing mitochondrial functional under induced stress-tolerance conditions.