Use of dill (Anethum graveolens L.) extract as a dye for the spores of Bacillus species

Finding environment-friendly alternatives to the use of toxic materials has recently become a major interest for the researchers in numerous fields. Malachite green dye known as a toxic material is used for staining of pervasive bacteria called Bacillus . In this study, an alcoholic extract of dill ( Anethum graveolens L.) leaves was used as an alternative to malachite green dye for staining of Bacillus species . Total chlorophylls content in extracts of dill leaves samples was measured by UV–Vis spectroscopy. The stability of the extract, the exposure time to on the steam bath, cold staining, and the total concentration of chlorophylls in the extract were optimised. The values of relative standard deviation and statistical analyses demonstrate that concentration of total chlorophylls in extracts was not significantly changed 72 h after extraction of samples if the extracts are stored in a dark place at room temperature. Results obtained from method optimisation revealed that spores of Bacillus species have been successfully stained by three to five drops of the dill leaves extract contained 1.78 μg/mL chlorophylls, when smears were treated with the extract for one minute at room temperature. The study shows that the dill ethanolic extract can be used as an eco-friendly natural replacement for the toxic malachite green dye for staining of Bacillus species . • This work reports a natural green dye extracted from dill plant. • An alternative dye to the toxic malachite green for spores staining of Bacillus. • Readily available material, low environmental hazards, and short time of staining. • Low consumption of energy and cheap reagents.