How bacteria develop antibiotic resistance.

A study from the Hebrew University of Jerusalem has shown how bacteria evolve and resist antibiotics. The scientists Using quantitative approaches from physics, biophysicists discovered a surprising way that bacteria can evolve resistance to antibiotics. 

 The new research published in the journal Science, researchers at the Hebrew University of Jerusalem report a startling alternative path to the evolution of resistance in bacteria.The bacteria evolve a sleeping mechanism after which the bacteria can then wake up and evolve resistance 20 times faster than normal -- at which point continuing to administer antibiotics won't kill the bacteria. 

 The results indicate that tolerance may play a crucial role in the evolution of resistance in bacterial populations under cyclic exposures to high antibiotic concentrations. To investigate this evolutionary process a group of biophysicists,exposed bacterial populations to a daily dose of antibiotics in controlled laboratory conditions, until resistance was established. 

By tracking the bacteria along the evolutionary process, they found that the lethal antibiotic dosage gave rise to bacteria that were transiently dormant, and were therefore protected from several types of antibiotics that target actively growing bacteria. 

 Once bacteria acquired the ability to go dormant, which is termed tolerance, they rapidly acquired mutations to resistance and were able to overcome the antibiotic treatment. First the bacteria evolved to sleep for most of the antibiotic treatment, and then this "sleeping mode" not only transiently protected them from the lethal action of the drug, but also actually worked as a stepping stone for the later acquisition of resistance factors.