Bacillus thuringiensis is a bacterium worth tracking in the environment because it is used as a pesticide for civilian purposes, and because it can be used as a simulant for the biological warfare agent, Bacillus anthracis. An in vitro selection and amplification technique entitled SELEX (Systematic Evolution of Ligands by EXponential enrichment) was used in order to identify a DNA aptamer sequence specific for BT. The 60 base aptamer was then coupled to fluorescent quantum dots (QD) which after binding to BT provide a sensitive and selective assay.