In Escherichia coli, cell division always plays a vital role in their proliferation when a mother cell is divided, and two identical daughter cells are formed. During the division process, a central component of protein, FtsZ, recruits more than 30 other divisome proteins to the mid-cell and builds a Z-ring structure. To regulate the Z-ring established at the proper site, the Min system: MinC, MinD, and MinE, oscillates from one cell pole to the opposite during the whole cell cycle. It is because that MinC is the inhibitor of preventing FtsZ assembly. In past research, people found that not only the Min-system shows the period oscillation in the cell, but also the FtsZ exhibits treadmilling dynamics to form the Z-ring. However, the majority of researchers focus the dynamics behaviors only on one protein among them, or the analysis methods they utilized only measured the average period/ frequency of one time period.

In our work, we developed an analysis procedure for investigating the dynamic behavior of FtsZ and MinD, as well as their dynamic relationship in the time-frequency domain over the entire cell cycle. Autocorrelation was utilized to determine the correlations and properties of each signal by itself. In order to gain instantaneous frequency of each protein signal to consult the correlation between two protein systems, we implemented the EEMD technique, which offers denoising signals a powerful tool, to decompose each IMFs of each protein signal and then used dynamic cross-correlation for analysis.

At last, despite the lack of a lucid result depicting the relationship between FtsZ and MinD proteins, we found that these two proteins may have a potentially in-phase synchronization between them in specific IMFs within their signals on the same-side cell poles during the cell cycle. However, the results cannot exclude the influence of bleeding and still need to be proved confidently by other supplementary control experiments as well.

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