Which is an example of gram-negative organisms?

Correct option is C

Ans. (c)
Sol. Vibrio cholerae is a gram-negative bacterium and is the causative agent of cholera. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane, which makes them more resistant to certain antibiotics. They appear pink/red after Gram staining.
Explanation of each option:
· (a) Listeria monocytogenes – A gram-positive bacillus, not gram-negative.
· (b) Streptococcus pneumoniae – A gram-positive diplococcus that causes pneumonia.
· (c) Vibrio cholerae – Correct answer. A gram-negative comma-shaped bacillus responsible for cholera.
· (d) Staphylococcus aureus – A gram-positive cocci that forms clusters.