Question

Which of the given statements are correct?
(I) Bacillus subtilis is Gram (+) bacteria
(ii) Escherichia coli is a Gram (-) bacterium
(iii) Washing of the Gram’s stain in Gram (-) bacteria is due to high lipid content of the cell wall, which gets dissolved in organic solvents like acetone
A.(I) and(ii)
B.(ii) and (iii)
C.(I) and (iii)
D.(I), (ii), and (iii)

Answer 1

Hint: Bacteria could be classified into two groups based upon the above reaction. Bacteria that retained the blue or purple color are known as Gram (+) bacteria (Ex: Bacillus subtilis). The bacteria which does not retain the stain and becomes colorless are called Gram (-) bacteria (Ex: Escherichia coli).
-Gram staining is a purple staining procedure to identify various bacteria types

Complete step by step answer:
- Christian Gram in 1884 stained bacteria with a weakly alkaline solution of crystal violet and then treated it with a 0.5% iodine solution. This was followed by washing with water and -Washing of the stain in Gram (-) bacteria is due to the high lipid content of their cell wall which gets dissolved in organic solvents like acetone, etc.
-Gram positive bacteria have a thick peptidoglycan layer while there is no outer lipid membrane. Gram negative bacteria on the other hand have a thin peptidoglycan layer with an outer lipid membrane covering
-Bacillus, Clostridium botulinum, Clostridium tetani, Clostridium difficile, Clostridium perfringens, Corynebacterium diphtheriae, and Corynebacterium jeikeium are some other examples of gram-positive bacteria.

Hence option D is correct.

Note:
-Gram-positive bacteria cause tremendous problems and are the focus of many eradication efforts worldwide. Meanwhile, Gram-negative bacteria have been developing dangerous resistance against antibiotics and are therefore classified by the CDC (center of disease control) as a more serious threat
-Some bacteria types such as mycobacteria (smallest bacteria variety) are not reliably stained due to their large lipid content of the peptidoglycan. Alternative staining techniques (Kinyoun or acid-fast stain) are therefore used that take advantage of the phenomenon of resistance to destaining after a lengthier initial staining