The Losick laboratory is no longer conducting research on Bacillus subtilis. We thank the NIH for 46 years of continuous support but have decided not to renew our grant on B. subtilis. Instead, we are focusing entirely on biofilm formation by the opportunistic pathogen Staphylococcus aureus, a cause of cause of numerous kinds of infections in humans. Biofilms are communities of bacteria in which cells adhere to each other and to a surface by an extracellular matrix composed of DNA, proteins, and/or polysaccharides. S. aureus (and methicillin-resistant strains in particular) forms biofilms by recycling cytoplasmic proteins and chromosomal DNA. The repurposed proteins, which are positively charged at the low pH under which biofilm formation takes place associate with the negatively charged cell surface. Our evidence indicates that the recycled chromosomal DNA (extracellular DNA) forms an electrostatic net with the protein coated cells holding them together. Recent work indicates that biofilm formation is triggered by a drop in the levels of the second messenger cyclic-di-AMP. Our findings point to cyclic-di-AMP as the intracellular signal for biofilm formation and a cyclic-di-AMP phosphodiesterase as an attractive target for drug development.