Motility modes of the parasite \textit{Trypanosoma brucei}*

The parasitic single-celled protozoan \textit{Trypanosoma brucei} causes African Sleeping Sickness, which is a fatal disease in humans and animals that threatens more than 60 million people in 36 African countries. Cell motility plays a critical role in the developmental phases and dissemination of the parasite. Unlike many other motile cells such as bacteria \textit{Escherichia coli} or \textit{Caulobacter crescentus}, the flagellum of \textit{T. brucei} is attached along the length of its awl-like body, producing a unique mode of motility that is not fully understood or characterized. Here, we report on the motility of \textit{T. brucei}, which swims using its single flagellum employing both rotating and undulating propulsion modes. We tracked cells in real-time in three dimensions using fluorescent microscopy. Data obtained from experiments using both short-term tracking within the field of view and long-term tracking using a tracking microscope were analyzed. Motility modes and swimming speed were analyzed as functions of cell size, rotation rate and undulation pattern.