Evidence for evolution - Resistant bacteria

Antibiotic resistance

Bacteria can evolve quickly because they reproduce at a fast rate. Mutations of bacteria produce new strains. Some bacteria might become resistant to certain antibiotics, such as penicillin, and cannot be destroyed by the antibiotic. The evolution of the bacteria is an example of natural selection and supports Darwin's theory of evolution.

Development of resistance

The main steps in the development of resistance are:

  1. random mutation occur in the genes of individual bacterial cells
  2. some mutations protect the bacterial cell from the effects of the antibiotic
  3. bacteria without the mutation die or cannot reproduce when the antibiotic is present
Diagram showing normal bacteria and one resistant bacterium


The number of resistant strains has increased, partly due to the overuse and misuse ofantibiotics. This has resulted in more infections that are difficult to control.

MRSA is methicillin-resistant staphylococcus aureus, and it is very dangerous because it is resistant to most antibiotics.

In order to reduce the rate of development of antibiotic resistant strains:

  • doctors should not prescribe antibiotics inappropriately, such as for the treatment of non-serious infections
  • patients should always complete the full course of antibiotics to ensure all bacteria are killed and none survive to mutate and form resistant strains
  • the agricultural use of antibiotics should be restricted
An agar plate containing penicillin

Penicillin was the first antibiotic to be produced on a mass scale in the 1940s. It is derived from the Penicillium fungus, shown here growing on an agar plate.

Many new types of antibiotics were discovered during the 1950s and 1960s, but more recently, this has slowed greatly.

Recent concerns of increasing resistance have created the need for new antibiotics, but they are costly and very slow to develop. Some scientists fear that we are fighting a losing battle against resistant bacteria, which may ultimately lead to people dying from simple infections, for example following operations.