ИСТИНА

Quorum sensing factors (QSF) are chemical compounds secreted by microorganisms depending on the culture density (Chen, Fink, 2006), that specifically regulate metabolic processes and cell differentiation (Gimeno et al., 1992; Lengeler et al., 2000). Three QSF are known for Saccharomyces сerevisiae: ammonia, triptophol and phenilethanol (Bassler, 2002; Wuster, Babu, 2009; Čáp et al., 2010). Here we show that carbon dioxide can also play the role of QSF for S.cerevisiae. Yeast cells (diploid wine strain VKM-J-542) from stationary phase culture were transfered to specific solid medium (3%_agar, 0.1%_CH3COONa, 0,1%_KH2PO4, 0.05%_MgSO4, +0.01%_CaCl2, 0.01%_NaCl, 0.5%_(NH4)2SO4 ). After the transfer, cells were still able to perform an additional cell cycle, with a 4-hour lag period before visible buds appeared (fig.1). Under these conditions carbon dioxide, exogenous or secreted by another, metabolically active yeast culture, shortened the budding lag period for 60-90 min (fig.1). The effect was not observed on complete media (YPD, beer wort) and was not associated with any carbon-dioxide-induced shift of the medium pH. The effective concentrations of carbon dioxide were found 0.5-4%, the sufficient duration of induction was 15-30 min. Therefore, we have shown that cell cycle progression in yeast could be regulated by concentration of exogenous carbon dioxide. As the latter could be produced by yeast cells from external colonies, the effect can be interpreted as a mechanism of cell-to-cell or colony-to-colony communication. As far as produced carbon dioxide concentration depends on producer cell density, it could be regarded as the first known quorum sensor which stimulates budding in yeast.