Albert stain applied to a smear from a throat swab shows club-shaped bacilli with bluish-black polar bodies against a green background. These metachromatic granules are composed chiefly of:
- A Polymetaphosphate ✓
- B Mycolic acid esterified with trehalose
- C Poly-beta-hydroxybutyrate
- D High molecular weight genomic DNA
Correct answer: A. Polymetaphosphate
Explanation
Volutin or metachromatic granules are storage depots of inorganic phosphate in the form of polymetaphosphate. Because they bind basic dyes differently from the rest of the cytoplasm, they take up toluidine blue or methylene blue in Albert stain as bluish-black bodies, giving the characteristic Babes-Ernst granule appearance. Poly-beta-hydroxybutyrate is a carbon reserve seen in Bacillus species and does not show metachromasia.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.