Newcombe-Experiment

The Newcombe experiment is an experiment conducted by Howard B. Newcombe and published in 1949, which shows that random mutations occur spontaneously in bacteria rather than in response to altered environmental conditions. Thus, Newcombe confirmed the result of the Luria-Delbrück experiment published by Salvador Edward Luria and Max Delbrück already in 1943, which also shows the occurrence of random mutations, even in the absence of selection mechanisms. Try to edit the source text

In the experiment, bacteria are incubated in a Petrischale for several hours and then transferred by means of the Replica Plate method to two other petri dishes treated with bacteriophages. While the first of the two petri dishes is directly incubated, the bacteria are distributed on the second with a drigal pan.

By accidental mutations at this time some bacterial cells are resistant to the attached bacteriophages. These individual cells can form new, resistant cell colonies after distribution over the entire Petrischale. Therefore, after the incubation on the second, distributed petrischale, much more surviving (ie resistant) bacteria can be observed than on the first Petrischale.

Thus Newcombe was able to demonstrate that the mutations are already present before selection pressure is applied by the bacteriophages. The alternative hypothesis, according to which bacteria develop only in response to the attack of the phage resistances, is refuted. Edit source text

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