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The National Academies: What You Need To Know About Infectious Disease

What You Need To Know About Infectious Disease

Bacteria

Bacteria are 10 to 100 times larger than viruses and are more self-sufficient. These single-celled organisms, generally visible under a low-powered microscope, come in three shapes: spherical (coccus), rodlike (bacillus), and curved (vibrio, spirillum, or spirochete).
Bacteria are ancient organisms. Evidence for them exists in the fossil record from more than 3 billion years ago.
Most bacteria carry a single circular molecule of DNA, which encodes (or programs) the essential genes for reproduction and other cellular functions. Sometimes they carry accessory small rings of DNA, known as plasmids, which enable specialized functions like antibiotic resistance. A broader term, antimicrobial resistance, includes resistance to drugs that treat infections, viruses, or parasites. Unlike more complex forms of life, bacteria carry only one set of chromosomes instead of two. They reproduce by dividing into two cells, a process called binary fission. Their offspring are identical, essentially clones with the exact same genetic material. When mistakes are made during replication and a mutation occurs, it creates variety within the population that could—under the right circumstances—lead to an enhanced ability to adapt to a changing environment. Bacteria can also acquire new genetic material from other bacteria, viruses, plants, and even yeasts. This ability means they can evolve suddenly and rapidly instead of adapting slowly.
 
Bacteria are ancient organisms. Evidence for them exists in the fossil record from more than 3 billion years ago. They have evolved many different behaviors over a wide range of habitats, learning to adhere to cells, make paralyzing poisons and other toxins, evade or suppress our bodies’ defenses, and resist drugs and the immune system’s antibodies. Bacterial infections are associated with diseases such as strep throat, tuberculosisstaph skin infections, and urinary tract and bloodstream infections. Methicillin-resistant Staphylococcus aureus (MRSA) infection—caused by a type of staph bacteria that has become resistant to many of the antibiotics used to treat ordinary staph infections—has become more prevalent in the last few years and is an area of focus for those working on antimicrobial resistance efforts.

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What do you know about infectious disease?

True or False: Antibiotics work by introducing an agent that resembles a disease-causing microbe, thus stimulating the body's immune system to recognize it as foreign, destroy it, and "remember" it, so that it can more easily identify and destroy any similar, disease-causing microbes that it later encounters.

  • Sorry, that’s incorrect.

    The above describes how vaccines work. Antibiotics work by either killing bacteria or stopping them from reproducing, allowing the body's natural defenses to eliminate the pathogens.

  • Correct!

    The above describes how vaccines work. Antibiotics work by either killing bacteria or stopping them from reproducing, allowing the body's natural defenses to eliminate the pathogens.

Infectious Disease Defined

Reservoir

An organism in which a parasite that is pathogenic for some other organism lives and reproduces without harming its host.

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