Question

A hypothetical bacterium swims among human intestinal contents until it finds a suitable location on the intestinal lining. Fecal matter from a human in whose intestine this bacterium lives can spread the bacterium, even after being mixed with water and boiled. The bacterium is susceptible to the penicillin family of antibiotics. It contains no plasmids and a lot of peptidoglycan. What will be the color of this bacterium after using the gram staining technique

Answer 1

Answer:

Bluish-purple color

Explanation:

It is given that the bacterium is susceptible to penicillin family of antibiotics. Penicillin only kills gram positive bacteria. It destroys them by inhibiting the peptidoglycan cell wall synthesis. Gram negative bacteria is not affected by penicillin because it has an outer membrane covering the cell wall. The lipopolysaccharide outer membrane does not allow penicillin to reach the cell wall. Hence, the bacteria in question is gram positive.

Gram positive bacteria is stained bluish-purple on gram staining because it retains the primary dye crystal violet after washing with alcohol. Whereas gram negative bacteria loses its outer membrane on washing with alcohol and picks up the secondary dye safranin, giving red color.

Hence, color of this bacterium will be bluish-purple after using gram staining technique.