Plasmids have a number of different functions. 

• They boost the organism’s survival rate by producing toxins that either kill other organisms or defend the host cell. 
• They contain at least one gene, most of which are beneficial to their host organisms. 
• They facilitate the replication process in bacteria. 
• They play a key role in helping the bacterium withstand occasional stressful conditions. 
• The smaller plasmids carry very few genes with a specific function instead of carrying large quantities of noncoding DNA. 
• Many plasmids with different functions can coexist in the same cell.