Robust Metabolic Responses to Varied Carbon Sources in Natural and Laboratory Strains of Saccharomyces cerevisiae

Understanding factors that regulate the metabolism and growth of an organism is of fundamental biologic interest. This study compared the influence of two different carbon substrates, dextrose and galactose, on the metabolic and growth rates of the yeast Saccharomyces cerevisiae. Yeast metabolic and growth rates varied widely depending on the metabolic substrate supplied. The metabolic and growth rates of a yeast strain maintained under long-term laboratory conditions was compared to strain isolated from natural condition when grown on different substrates. Previous studies had determined that there are numerous genetic differences between these two strains. However, the overall metabolic and growth rates of a wild isolate of yeast was very similar to that of a strain that had been maintained under laboratory conditions for many decades. This indicates that, at in least this case, metabolism and growth appear to be well buffered against genetic differences. Metabolic rate and cell number did not co-vary in a simple linear manner. When grown in either dextrose or galactose, both strains showed a growth pattern in which the number of cells continued to increase well after the metabolic rate began a sharp decline. Previous studied have reported that O2 consumption in S. cerevisiae grown in reduced dextrose levels were elevated compared to higher levels. Low dextrose levels have been proposed to induce caloric restriction and increase life span in yeast. However, there was no evidence that reduced levels of dextrose increased metabolic rates, measured by either O2 consumption or CO2 production, in the strains used in this study

Robust metabolic responses to varied carbon sources in natural and laboratory strains of Saccharomyces cerevisiae.

Understanding factors that regulate the metabolism and growth of an organism is of fundamental biologic interest. This study compared the influence of two different carbon substrates, dextrose and galactose, on the metabolic and growth rates of the yeast Saccharomyces cerevisiae. Yeast metabolic and growth rates varied widely depending on the metabolic substrate supplied. The metabolic and growth rates of a yeast strain maintained under long-term laboratory conditions was compared to strain isolated from natural condition when grown on different substrates. Previous studies had determined that there are numerous genetic differences between these two strains. However, the overall metabolic and growth rates of a wild isolate of yeast was very similar to that of a strain that had been maintained under laboratory conditions for many decades. This indicates that, at in least this case, metabolism and growth appear to be well buffered against genetic differences. Metabolic rate and cell number did not co-vary in a simple linear manner. When grown in either dextrose or galactose, both strains showed a growth pattern in which the number of cells continued to increase well after the metabolic rate began a sharp decline. Previous studied have reported that O₂ consumption in S. cerevisiae grown in reduced dextrose levels were elevated compared to higher levels. Low dextrose levels have been proposed to induce caloric restriction and increase life span in yeast. However, there was no evidence that reduced levels of dextrose increased metabolic rates, measured by either O₂ consumption or CO₂ production, in the strains used in this study

Metabolic rate, growth and respiratory quotient (RQ) of BY and RM grown in YP with 2% dextrose.

<p>Graphs are plotted using the means and sem of 6 groups for the CO₂/O₂ measurements and for 3 groups for the growth measurements. Cell number per ml for <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030053#pone-0030053-g001" target="_blank">figures 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030053#pone-0030053-g002" target="_blank">2</a> were calculated based on converting an optical density reading to an estimated cell number.</p

Relative metabolic rate of BY (3A) and RM (3B) grown in YP with a starting concentration of 0.1 to 4% dextrose based on CO₂ production. Figures 3 –6 are plotted using the means and sem of 6 groups.

<p> The metabolic rate data were normalized to a value of 1.0 at the 2^nd metabolic reading.</p

Relative metabolic rate of BY (4A) and RM (4B) grown in YP with a starting concentration of 0.1 to 4% dextrose based on O₂ consumption.

<p>Relative metabolic rate of BY (4A) and RM (4B) grown in YP with a starting concentration of 0.1 to 4% dextrose based on O₂ consumption.</p

Metabolic rate, growth and RQ of BY and RM grown in YP with 3% galactose.

<p>Graphs are plotted using the means and sem of 6 groups for the CO₂/O₂ measurements and for 3 groups for the growth measurements.</p

RQ of BY (4A) and RM (4B) grown in YP with a starting concentration of 0.1 to 4% dextrose.

<p>RQ of BY (4A) and RM (4B) grown in YP with a starting concentration of 0.1 to 4% dextrose.</p