Final answer:
R-plasmids are unique because they can transfer between cells of the same or different species, allowing for the spread of antibiotic resistance in bacterial communities.
Step-by-step explanation:
R-plasmids are plasmids that contain genes encoding proteins that make a bacterial cell resistant to one or more antibiotics.
They are unique because they are able to transfer between cells of the same species and between cells of different species, allowing for the spread of antibiotic resistance in bacterial communities.
R-plasmids commonly contain multiple genes conferring resistance to multiple antibiotics.