Poly(methacrylic acid) enhances emission of dye stain extracted from bacterial spores: Fluorimetric quantitation in aqueous samples

A new fluorometric procedure is demonstrated for fast detection of dormant bacterial endospores in suspension. The method is based on quantitative uptake of the cationic dye stain malachite green (MG) by permeabilized spores. Specifically bound stain is extracted from the spores into poly(methacrylic acid) (PMAA) acidic solution. The steady-state fluorescence enhancement of MG in buffered PMAA-citrate is then employed for determination of dye uptake by spores at the nanogram scale. The assay tolerates the presence of anions, surfactants and other potentially masking species, that may be present in environmental samples. The analytical procedure is simple and allows sensitive (<105 ml−1) identification of bacterial spores in aqueous samples within 1–2 h, in presence of possible masking factors, such as salts (buffers), surfactants and neutral particles.