penicillin

• • Prevents bacterial cell walls from developing properly by inhibiting the synthesis of peptidoglycan (a mesh-like substance made up of sugars and amino acids) 
• • Peptidoglycan ensures that the bacterial cell is osmotically balanced
• • Causes the bacterial cell walls to weaken, resulting in the death of the cell
• • Doesn't affect the host of that bacteria is residing in as animals don't produce peptidoglycan