While both bacteria and viruses are capable of making us sick, they are very different microbes. Bacteria are living organisms that produce energy and are capable of independent reproduction. Viruses are not cells but particles of DNA or RNA encased within a protective shell. They do not possess all of the characteristics of living organisms. Viruses must rely on other organisms in order to reproduce because they do not possess the organelles needed to replicate. Bacteria are typically larger than viruses and susceptible to antibiotics. Antibiotics do not work against viruses and viral infections.