Quantitative analysis of time-series fluorescence microscopy using a spot tracking method: application to Min protein dynamics

Abstract

The dynamics of MinD protein has been recognized as playing an important role in the accurate positioning of the septum during cell division. In this work, spot tracking technique (STT) was applied to track the motion and quantitatively characterize the dynamic behavior of green fluorescent protein-labeled MinD (GFP-MinD) in an Escherichia coli system. We investigated MinD dynamics on the level of particle ensemble or cluster focusing on the position and motion of the maximum in the spatial distribution of MinD proteins. The main results are twofold: (i) a demonstration of how STT could be an acceptable tool for MinD dynamics studies; and (ii) quantitative findings with parametric and non-parametric analyses. Specifically, experimental data monitored from the dividing E. coli cells (typically 4.98 ± 0.75 µm in length) has demonstrated a fast oscillation of the MinD protein between the two poles, with an average period of 54.6 ± 8.6 s. Observations of the oscillating trajectory and velocity show a trapping or localized behavior of MinD around the polar zone, with average localization velocity of 0.29 ± 0.06 µm/s; and flight switching was observed at the pole-to-pole leading edge, with an average switching velocity of 2.95 ± 0.31 µm/s. Subdiffusive motion of MinD proteins at the polar zone was found and investigated with the dynamic exponent, α of 0.34 ± 0.16. To compare with the Gaussian-based analysis, non-parametric statistical analysis and noise consideration were also performed.

Mapping out Min protein patterns in fully confined fluidic chambers

“…In addition, the reduction in wavelength was accompanied by a very large reduction in the wave propagation velocity. Note that the measured velocity in the highly viscous media was similar or even smaller than the one measured in vivo (Unai et al, 2009) (see also the supporting information in [Bonny et al, 2013]). It is thus unlikely that additional increases in viscosity can bring both the characteristic length scale and the propagation velocity of the system in vitro to the in vivo values.…”

The effect of boundary conditions on the mesoscopic lattice Boltzmann method: Case study of a reaction–diffusion based model for Min-protein oscillation

“…It is reasonable to say that the LBM approach could provide an alternative fast computational tool for studying Min-protein oscillation. It provides numerical results which are in qualitative agreement with experimental results [12,17,18]. However, optimization treatment, especially regarding boundary conditions, could be a very important issue.…”

“…This implies that MinE tries to prevent septum proteins from being formed at the cell middle site and tries to suppress the inhibitor, MinD, from this region. To validate this conclusion, we compared the numerical results to the experimental data compiled by our group members [17,18]. When we compared the LBM results with the experimental results, they were in qualitative agreement.…”

“…The method was shown to recover the Howard model at the macroscopic level [15,16]. In addition, the numerical results from this technique were consistent with experimental results [12,17,18]. Hence the LBM approach is an effective alternative tool for studying Min-protein oscillation, which naturally deals with particle dynamics.…”

Biophysical approach for studying the MinD protein dynamics and energy landscape: a novel use of the spot tracking technique

“…In addition, Unai et al quantitatively investigated MinD dynamics on the level of particle cluster. Using a spot tracking technique (STT) [11] -which shares a common feature with single particle tracking [12,13] they focused on the position and motion of the maximum in the spatial distribution of MinD proteins. STT results quantitatively provide us with information on position alterations and time sequences which can be used to analyze the GFP-MinD dynamics.…”