Dyestuffs from four Nigerian plants were extracted and their staining ability on some species of bacteria and moulds were determined. The dyestuffs were extracted using water and organic solvents. Acetic acid treatment of the extracts increased the ability of the extract to stain both bacteria and moulds. Treatment with ammonium hydroxide reduced the staining of the plant extracts except the zobo (Hibuscus sabderiffa) extract. The best staining result was observed with uhe (Pterocarpus osun) extracts. Annato (Bixa orellana) and zobo extracts had moderate effect; whereas Lalle (Lawsonia inermis) showed little or no staining potential. The stains however had greater affinity for moulds than bacteria. The results obtained indicate that extracts with good staining ability have the potential for use in the morphological identification of moulds and in diagnostic bacteriology.
Key words: Plant extracts, staining, moulds, bacteria.
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