Figure 4From: Measurement of microbial activity in soil by colorimetric observation of in situ dye reduction: an approach to detection of extraterrestrial lifeReduction of XTT dye by the heat-treated control soil and the life-positive Idaho red sand Data points represent: (●), sterilized soil; and (■), live soil. Data points are means of three replicates, +/- standard deviation. Dye-only controls showed no reduction over the time course of the experiment. AU = Absorbance UnitsBack to article page