The Modell lab at Johns Hopkins School of Medicine studies CRISPR-Cas9 biology and bacterial mechanisms of phage defense more broadly. Specifically, we explore how CRISPR-Cas9 systems function in nature to provide their bacterial hosts with adaptive immunity against phages and plasmids. More recently, we have begun identifying and characterizing new phage defense systems, and we believe this knowledge will be crucial for the development of phage therapies for antibiotic-resistant bacterial infections. We ask fundamental biological questions with an array of approaches including genetics, genomics, molecular biology, biochemistry, bioinformatics and live-cell microscopy. Our studies provide insights into (i) bacterial decision-making and stress responses, (ii) the emerging field o