Live-cell Imaging of Neisseria meningitidis Microcolony Dispersal Induced by Lactate or Other Molecules.

To efficiently colonize the nasopharyngeal epithelium, the human restricted pathogen Neisseria meningitidis follows a multistep adhesion cascade. First, the bacteria adhere to host cells and aggregate into spherical shaped structures called microcolonies. Several hours later, single bacteria start dispersing from the microcolonies and form a monolayer on top of the host cells. Once in proximity to host cells meningococci can adhere tightly to the epithelial surface or become internalized. This can eventually result in invasion of the mucosal surfaces and gain access to the bloodstream, causing a life-threatening disease. Lactate, a metabolite derived from human epithelial cells, has been previously shown to induce rapid dispersal of N. meningitidis from microcolonies. Here, we describe a host-cell free method based on live-cell imaging to examine the effect of host derived lactate on the timing of N. meningitides microcolony dispersal. Although in this protocol we use lactate, it can be easily modified to test the effects of other molecules.