Final answer:
Cross-linking in peptidoglycan fibers significantly strengthens bacterial cell walls by forming a mesh-like structure through peptide bonds between amino acids, providing resistance to osmotic pressure and shape maintenance.
Step-by-step explanation:
Cross-linking in peptidoglycan fibers enhances the structural integrity of bacterial cell walls. The peptidoglycan, primarily composed of the polysaccharides N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), relies on cross-links to provide tensile strength. These linkages occur through peptide bonds between the amino acids attached to NAM molecules, interconnecting the polysaccharide chains into a mesh-like layer. The process strengthens the cell wall, making it resistant to osmotic pressure and helping to maintain the cell's shape. Furthermore, some antibiotics target these cross-links by mimicking D-amino acids, thereby hindering cell wall synthesis and compromising bacterial integrity.