Microbiology Practice Exam

Plasmids are small, circular DNA molecules found in bacteria that exist independently of the chromosomal DNA. Their primary function is to provide genetic advantages to bacteria, one of the most significant being the ability to confer antibiotic resistance. When bacteria acquire plasmids that carry resistance genes, they can survive exposure to antibiotics that would typically kill or inhibit them. This trait is crucial for bacterial survival in environments where antibiotics are present, leading to the spread of resistant strains.

In addition to providing antibiotic resistance, plasmids can carry genes that enable bacteria to metabolize unusual substances, produce virulence factors, or engage in conjugation (the transfer of genetic material between bacteria). While plasmids can play roles in other cellular processes, such as contributing to the replication of their own DNA or facilitating protein synthesis related to their specific genes, these functions are secondary to their role in promoting antibiotic resistance, especially in the context of evolutionary pressure within microbial communities.