Final answer:
Polymyxin inhibits bacterial growth by targeting the outer and inner membranes of gram-negative bacteria, which is different from other antibiotics that may target protein synthesis or cell wall biosynthesis.
Step-by-step explanation:
The question pertains to which of the listed antibiotics inhibits bacterial growth by targeting a cellular component different from those targeted by the others. According to the information provided, polymyxins, such as polymyxin B, are known to function by interacting with the lipopolysaccharide component of the outer membrane of gram-negative bacteria, leading to disruption of both outer and inner bacterial membranes. This mode of action is distinct from those of other antibiotics that commonly target protein synthesis or cell wall biosynthesis, confirming that polymyxins inhibit bacterial growth by blocking cellular targets differently from the others listed.