Unlocking the Secrets of Multi-Flagellated Propulsion

In this work, unique high-speed imaging platforms and an array of theoretical analysis methods are used to thoroughly investigate eukaryotic multi-flagellated propulsion using Tritrichomonas foetus as a test case. Through experimental observations through our imaging system with superior resolution and capture rate exceeding that of previous studies, it was discovered for the first time that the T. foetus employs a strategy similar to that of the “run and tumble” strategies found in bacteria and Chlamydomonas; it has two distinct flagellar beating patterns that result in two different body swimming motions, linear and turning swimming.

These two flagella patterns were then analyzed for the first time using two theoretical analysis methods that are often used to analyze uni-flagellated organisms; the Resistive Force Theory (RFT) and the Regularized Stokeslet Method (RSM). These theories were compared to uncover the more accurate method. Results showed that our modified-RFT model out-performed the RSM model. Due to these results, the quantitative analysis of the motion of each flagellum for both the swimming motions were carried out using the RFT method for the first time on a multi-flagellated cell, in both the 2-D and 3-D case.

Digital Holographic Microscopy was used to produce the 3-D trajectory of the T.foetus for the first time. Through this method it was possible to for the first time, quantitatively analyze the thrust and energy contributions of each flagella in each direction. We find out that the turning motion dissipates approximately half as much energy as the linear swimming motion which leads to the belief that the motion is more energy efficient. The energy results coupled with the thrust results show the highly coordinated nature of multi-flagellated propulsion. Through this RFT model, it was observed that the propulsive force of the T.foetus is comparable to that of other eukaryotes with varying numbers of flagella like the sperm and Chlamydomonas, suggesting that higher thrust generation is not necessarily the goal of multi-flagellated propulsion, but these strategies result in greater maneuverability or sensing. Results from this study may serve as inspiration for biorobots due to the organism’s ideal size and finely controlled multi-flagellated propulsion.