Background
Nitric oxide (NO), a well-known signaling molecule in eukaryotic organisms, has recently been implicated in the development of bacterial biofilms. Biofilms are surface-bound, matrix-encapsulated, multicellular communities that are extremely resistant to antibiotic treatments. In addition to being important in many aquatic, industrial, and environmental processes, biofilms are responsible for ~60% of all human non-viral infections. NO has been reported to disperse bacterial biofilms through regulation of intracellular cyclic-di-guanosine monophosphate (c-di-GMP) concentrations. C-di-GMP is a tightly regulated second messenger signaling molecule that is tightly correlated with biofilm formation. When we began our work, however, the NO sensor(s) and biochemical signalling pathway(s) that regulate c-di-GMP concentrations was unknown.