LuriaDelbrückeksperimentet

LuriaDelbrücke refers to a seminal experiment in microbial genetics performed independently by Salvador Luria and Max Delbrück in the early 1940s. Their work was crucial in demonstrating that genetic mutations in bacteria arise spontaneously and are not induced by selective pressure. This challenged the prevailing Lamarckian view of inheritance, which suggested that acquired characteristics could be passed down.

Luria and Delbrück used bacteriophages (viruses that infect bacteria) and their host bacteria, specifically Escherichia coli. They observed that when a large population of bacteria was exposed to a bacteriophage, some bacteria would resist infection and survive, while others would be killed. The key insight came from developing a method to test for the presence of pre-existing resistance in the bacterial population before phage exposure.

Using a technique called replica plating, they showed that the resistant bacteria were present in the original population at a low frequency, even before the bacteriophages were introduced. This meant that the mutations conferring resistance had occurred randomly and spontaneously. The bacteriophages then acted as a selective agent, killing the non-resistant bacteria and allowing the pre-existing resistant ones to proliferate. This groundbreaking discovery provided strong evidence for the random nature of mutation and the Darwinian mechanism of natural selection at the microbial level, significantly advancing the field of molecular biology and genetics.