Researchers from Konstantin Severinov's laboratory have shown what luck has to do with bacterial cells acquiring and retaining small DNA molecules called plasmids in spite of the countering action of the CRISPR-Cas defense. Genes carried on plasmids provide bacteria with resistance to antibiotics—a phenomenon plaguing people around the world. The findings provide insights on how to effectively deal with the spread of antibiotic resistance by harnessing the cellular defense system called CRISPR-Cas. The paper is published in the Proceedings of the National Academy of Sciences.