Peptidoglycan is a complex polymer that forms a crucial part of the cell wall in most bacteria. It provides structural support and protection, helping to maintain the shape of the bacterial cell. Composed of sugar chains cross-linked by short peptides, peptidoglycan is essential for the survival of bacteria in various environments. The thickness of peptidoglycan varies between different types of bacteria, contributing to their classification as either Gram-positive or Gram-negative. In Gram-positive bacteria, the peptidoglycan layer is thick, while in Gram-negative bacteria, it is thinner and located between an outer membrane and the inner cell membrane.