Bacterial cell walls are rigid structures that provide shape and protection to bacterial cells. They are primarily composed of a polymer called peptidoglycan, which consists of sugars and amino acids. This unique structure helps bacteria maintain their integrity in various environments and prevents them from bursting due to osmotic pressure. The composition of bacterial cell walls can vary between different types of bacteria. Gram-positive bacteria have thick layers of peptidoglycan, while Gram-negative bacteria have a thinner layer and an outer membrane. This difference is crucial for determining how bacteria respond to antibiotics and their overall susceptibility to environmental stresses.