Abstract: Because of the small size of bacterial cells, the mysteries of their subcellular structure, dynamics and cooperativity are well suited to single-molecule and super-resolution investigations. Our lab has been developing new methods to locate, track and analyze single molecules to answer fundamental, unanswered questions in live bacterial cells. I will discuss how we are measuring and understanding the dynamical interactions essential for DNA replication and mismatch repair in living Bacillus subtilis cells, as well as our ongoing work to extend our targets from single cells to microbial communities. Overall, our results provide fundamental insight of relevance to human health and disease.