AAT Bioquest

What is the difference between bacteria and viruses?

Posted June 1, 2020


Bacteria and viruses differ in many ways, such as structure, size, pathogenicity as well as response to medications.

  • Structure: Bacteria are single-celled, living organisms, which have all the components necessary to survive and reproduce outside a living host. Viruses have no cell wall or organelles, who are described as “organisms at the edge of life”. Although viruses have genes, they do not have a cellular structure to perform their own metabolism, thus requiring a host cell to make new products.
  • Size: Bacteria are about 1000 nm in size, which are visible under light microscope. Viruses are much smaller, usually about 20-400 nm, which can be visualized by electron microscope.
  • Pathogenicity: Most bacteria are beneficial for our good health and the health of earth’s ecosystems, with only 1% of bacteria causing diseases. Most viruses cause diseases.
  • Response to medications: Antibiotics may be used to treat some bacterial infections, but they do not work against viruses. Antivirals, on the other hand, are engineered to treat viral infections, which are not effective against bacteria.
Additional resources

MycoLight™ Live Bacteria Fluorescence Imaging Kit

MycoLight™ Flow Cytometric Live Bacteria Assay Kit

Kohanski, M. A., Dwyer, D. J., & Collins, J. J. (2010). How antibiotics kill bacteria: from targets to networks. Nature Reviews Microbiology, 8(6), 423-435.

Almand, E. A., Moore, M. D., & Jaykus, L. A. (2017). Virus-bacteria interactions: an emerging topic in human infection. Viruses, 9(3), 58.