What is a primary function of plasmids in bacteria?

Plasmids play a crucial role in bacteria, primarily by carrying genes that can provide additional functions or advantages, such as antibiotic resistance. These small, circular pieces of DNA are separate from the bacterial chromosomal DNA and can replicate independently. When plasmids contain genes that confer resistance to antibiotics, they can be readily transferred between bacteria through a process called horizontal gene transfer. This ability enhances the survival of bacteria in environments with antibiotic pressure, making plasmids integral to the evolution and adaptation of bacterial populations.

In contrast, the other options describe functions that are not primarily associated with plasmids. While bacteria do engage in cellular metabolism and can synthesize proteins, these processes are primarily governed by their chromosomal DNA. Biofilm formation is a complex process that involves multiple cellular structures and signaling pathways, rather than being directly attributed to plasmids. Therefore, the primary function of plasmids is indeed related to carrying genes for antibiotic resistance and other traits that can provide competitive advantages to bacteria in various environments.