Question

The main difference between gram-positive & gram-negative bacteria is in
A. Number of cilia
B. Presence of plastids
C. Cell wall composition
D. Types of ribosomes

Answer 1

Hint: Bacteria are the sole members of kingdom Monera. They are unicellular, microscopic organisms that lack a true nucleus (hence called prokaryotic organisms). Bacteria can be of two types: gram-positive or gram-negative which is decided on the basis of the gram staining method.

Complete answer: There are a lot of differences between the two groups which are listed below in the table:

	Basis	Gram-Negative bacteria	Gram-Positive bacteria
1.	Cell Wall composition	Has a thin peptidoglycan layer (single-layer).	Has a thick peptidoglycan layer (multi-layer).
2.	Chemicals	Teichoic acid is absent and has 20-30 percent lipids.	Teichoic acid is present and has negligible lipids.
3.	Cell wall texture	Has a double layer which is wavy.	Has a single layer that is smooth.
4.	Cell wall width	8-10 nm	20-80 nm
5.	Gram staining	Do not hold the crystal violet stain after being washed with alcohol.	Holds the crystal violet stain even after being washed with alcohol.
6.	Microscopic view	Appear pink in colour.	Appear dark purple in colour.

Among all these differences the most important differentiating factor between the two types is the cell wall composition in them.
So, the correct answer is option C, i.e., Cell wall composition.

Note: It is important to note that both types of bacteria produce certain toxins. The gram-positive bacteria are reported to produce only exotoxins, on the other hand, gram-negative bacteria process both endotoxins as well as exotoxins.