Much of biological motion is driven by Molecular Motors. Motors are nanoscale machines that generate tiny force to walk along protein filaments inside the cell. As they walk, they carry different "cargoes". One example of a cargo is bacteria that are enclosed inside a "Phagosome" and transported to cellular locations where they can be killed in an acidic environment. We are now able to measure the number of motors transporting single phagosomes inside cells using an optical trap.
Our results suggest that a decisive switch in a phagosome's fate is because of the formation of cholesterol-rich domains called Lipid rafts on the phagosome. Motors geometrically cluster into these rafts, and by doing so are able to work cooperatively in large teams. I will discuss the biophysical evidence for this clustering, and the implications to infection by Mycobacterium Tuberculosis and Leishmania.