The Use of Plant Dyes for Microbial Staining and Identification: An Eco-friendly and Non-Toxic Alternative Method

Staining of microbial cells is a very important procedure in microbial identification. Cells need to be fixed and stained to increase visibility, accentuate morphological features and for preservation. The study was carried out to explore the efficiency of natural dyes from four different plants which can be used to stain bacterial cells.

Plant extracts which has been processed into dyes namely Enantia chlorantha, Harungana madagascariensis, Sphenocentrum jollyanum and Sarcocephalus latifolius were obtained from Botany Department, Obafemi Awolowo University, Nigeria. They were used to stain some Gram positive and negative bacterial cells. The dyes were extracted with Soxhlet apparatus using ethanol as solvent.

The physiological features observed were compared with features of microorganisms that were stained with synthetic dyes when viewed under Olympus microscope at X100.

The dye from Harungana madagascariensis imparted its dark brown colour on the microbial cells within few seconds of application. A dark yellowish-brown dye from Sarcocephalus latifolius imparted a pinkish coloration on Gram negative organisms. Dye from Enantia chlorantha imparted light brownish colouration on Gram positive and light pink on Gram negative organisms. The dark yellow dye from Sphenocentrum jollyanum bark imparted greenish brown colouration on both Gram positive and light brown on Gram negative organisms. The best of the four dyes, Enantia chlorantha exerted a high fastness property which was seen when the slides were viewed.

The dyes from the plants when oxidized could be used as a suitable substitute for staining microorganisms. The procedure is simple, cheap, readily available and can be prepared easily. The applications and use of these natural dyes are found to be biodegradable, non-toxic and eco-friendly.