Question

What are three differences between Gram-positive and Gram-negative cells? (*Not including properties associated with the Gram-stain). Provide an explanation, or description, for each.

Answer 1

Answer :

Gram reaction divides bacteria into gram positives and gram negatives depending on the color retained in the staining procedure. However, there are many major and minor differences between these two group of bacteria apart from differences in cell wall structure which are responsible for their gram reactions.

Some of the differences are as follows :

1. Gram positive bacteria have Teichoic acid in their cell wall whereas it is absent in gram negative bacteria. Teichoic acids are bacterial copolymers of glycerol phosphate and carbohydrates that are linked through phosphodiester bonds. Teichoic acids affect the bindings of extracellular molecules on bacterial cell and thereby offer protection to the bacteria.
2. Gram Positive bacteria do not have an outer membrane like gram negative bacteria. Hence, Gram positive bacteria also do not have porins which are present in the outer membrane of gram negative bacteria. Porins play an important role in transport of water molecules and are responsible for making bacteria resistant to surfactants and detergents.
3. Gram positive bacteria primarily produce Exotoxins whereas Gram negative bacteria can produce endotoxins as well as exotoxins. The outer layer of gram negative bacteria itself is a toxin when it enters blood stream of humans or other animals. Exotoxins are toxins that are secreted out of the body of the bacteria whereas Endotoxins are available within the body of the bacteria and are released when bacterial cell is lysed.
4. Gram Positive bacteria are more sturdy and show greater resistance to physical disruption as compared to Gram Negative bacteria. This is also a function of their cell wall.