It is the selective action of antibiotics against bacteria that make them useful in the treatment of infections while at the same time allowing the host to live another day. Already a subscriber?
Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? The cell walls of plants, for example, are made from cellulose. The cell walls of algae are highly variable. Algae cell walls can be made of cellulose, xylan, silica, carrageenan or a variety of other materials.
The cell walls of most fungi are made from chitin. Composition of the cell wall in the archaea is more diverse. Within bacteria, there are two types of bacterial cell walls. Gram-positive bacteria have a peptidoglycan layer on the outside of the cell wall. Gram-negative bacteria have peptidoglycan between membranes. Penicillin works best on gram-positive bacteria by inhibiting peptidoglycan production, making the cells leaky and fragile.
The cells burst open and are much easier for the immune system to break down, which helps the sick person heal more quickly. Human cells do not contain peptidoglycan, so penicillin specifically targets bacterial cells. Other antibiotics target different molecules that inhibit bacterial growth while leaving human cells undamaged.
Sulfa antibiotics target a specific enzyme that inhibits bacterial growth. Tetracycline antibiotics bind to bacterial ribosomes that are responsible for protein production and inhibit bacterial protein synthesis. Ciprofloxacin, one of the strongest antibiotics, attacks bacterial DNA replication while leaving human cellular DNA unaffected.
Others, known as broad-spectrum antibiotics, attack a wide range of bacteria, including ones that are beneficial to us. There are two main ways in which antibiotics target bacteria. They either prevent the reproduction of bacteria, or they kill the bacteria, for example by stopping the mechanism responsible for building their cell walls. The introduction of antibiotics into medicine revolutionised the way infectious diseases were treated. Between and , average human life expectancy jumped by eight years, with antibiotics used to treat infections that were previously likely to kill patients.
Today, antibiotics are one of the most common classes of drugs used in medicine and make possible many of the complex surgeries that have become routine around the world. If we ran out of effective antibiotics, modern medicine would be set back by decades.
Relatively minor surgeries, such as appendectomies, could become life threatening, as they were before antibiotics became widely available. Antibiotics are sometimes used in a limited numbers of patients before surgery to ensure that patients do not contract any infections from bacteria entering open cuts.
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