* Peptidoglycan is a unique and essential component of bacterial cell walls.

* It's a complex polymer made of sugars and amino acids that forms a mesh-like structure.

* This structure provides rigidity and shape to the bacterial cell, protecting it from osmotic pressure.

Important Note: While most bacteria have peptidoglycan in their cell walls, some exceptions exist. Mycoplasmas, for example, lack a true cell wall and instead have a membrane-like structure.