Evaluation of Saccharomyces cerevisiae Yeast Vacuoles in Conjunction with Several Lysosomal Fluorescent Dyes as Potential Biosensors to Detect Toxicants of Military Interest

Saccharomyces cerevisiae vacuoles having the functionality of lysosomes with regard to uptake of toxicants from the environment followed by acidification and/or vacuolar membrane swelling were evaluated with several lysosome-specific fluorescent dyes to determine if any of the toxicants on the U.S. Army’s list of chemicals for testing after water purification at or below the human lethal concentration (HLC) would invoke a yeast cell fluorescence response. Preliminary data suggest that four of the nine chemicals on the Army’s list, namely sodium azide, mercuric chloride, nicotine, and phenol, were detectable by fluorescence at the HLC in water using carboxy-DCFDA or MDY-64 within 5 to 90 minutes of chemical exposure using quantitative fluorometric microplate analyses and microscopic fluorescence image analysis. The present work provides proof of concept for further studies to determine if other lysosomal dyes could be used to take advantage of yeast and their vacuoles as robust and inexpensive biosensors with long shelf lives in the dehydrated state for detection of a broader array of environmental toxicants. Interestingly, the yeast were also shown to be sensitive to hyperosmotic salt concentrations using LysoTracker Green.