Three-dimensional modelling of trypanosome cells reveals characteristic morphologies correlating to the species-specific motility behaviour.

<p>The parasites were harvested from infected mice and the cell surface was fluorescently labelled with sulfo-NHS dyes. On the left of each panel representative surface-rendered models of fluorescently surface-labelled trypanosome cells are shown. The fluorescence labelling allows the simultaneous visualisation of the cell body and the flagellar membrane. The complete trace of the flagellum (yellow) attached along the cell body (grey) is shown in the three-dimensional representation. The model was orientated to show the view onto the posterior tip, allowing to evaluate the course of the flagellar attachment along the cell body, starting at the exit from the flagellar pocket at the top of the cell and tracing it towards the anterior end. A selection of 3D-models is presented to illustrate the variety of shapes the trypanosomes adopt, based on their cellular waveform. The numbers present the average length of the trypanosomes L_av (n = 100) and the average maximum width of the cells W_av (n = 100) as measured in video stills (see <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1005448#ppat.1005448.g001" target="_blank">Fig 1</a>). The actual length L, volume V and cells surface area A of the surface-rendered models are given below in grey letters. The first cell in each row was chosen for surface-modelling. (A) Examples of normal waveform <i>T</i>. <i>vivax</i> IL 1392 cells. The flagellum is attached in a shallow 180° right hand turn. (B) <i>T</i>. <i>vivax</i> IL 2136 normal waveforms. The flagellum exhibits a similar course to IL 1392 running along a slightly stiffer cell body. (C) The <i>T</i>. <i>brucei</i> ILTat 1.4 strain typically shows a more prominent 180° right handed turn around the posterior third of the cell body. (D) The pleomorphic <i>T</i>. <i>brucei</i> AnTat 1.1 strain slender and stumpy forms. The three cells on the right are short stumpy trypanosomes that are characterised by the absence of a free part of the flagellum. The slender forms show a similar 180° right hand turn when compared to ILTat 1.4 in C). Morphometric data are for the slender stage (E) <i>T</i>. <i>evansi</i> reveals a curlier waveform than <i>T</i>. <i>brucei</i> while the flagellum turns completely (360°) around the cell body.(F) <i>T</i>. <i>congolense</i> IL 1180 cells are small with a stiff cell body and a flagellum running along it in a relatively straight course. (G) <i>T</i>. <i>congolense</i> KETRI 3827 is larger than the IL 1180 strain, but reveals the same characteristic waveform.