Abstract:
Cell size is an important factor for survival, that microorganisms tune to their environmental needs.
Nevertheless, all microorganisms exhibit large heterogeneity in cell size even when experiencing
homogenous environmental conditions. This heterogeneity is in part due to the stochastic nature of the
complex processes that control cellular growth and division dynamics. It is also limited by cellular
mechanisms that operate in concert to prevent size divergence over time. In this talk, I will discuss the
contribution of one of these mechanisms, namely the Min proteins, to cell size regulation in the bacterial
model organism E. coli. The Min proteins interactions and diffusion within the cell create oscillations
along the cell’s length that aid in the formation of the division ring at mid-cell. Previously, it was assumed
that the Min proteins’ function is limited to the localization of the division ring along the cell’s long axis.
However, the dynamical pattern of these oscillations is sensitive to the cell length, which allows the Min
proteins to coordinate the initiation time of the division ring formation with the cell length and as a
result can help regulate cell size. Our results reveal how the pattern of the Min proteins oscillations
change with cell size and how that determines the timing of division ring formation and ultimately cell
size at subsequent divisions. The contribution of the Min proteins to cell size regulation is one that
enables a cell born smaller than its sister during the “supposedly” symmetric division, to grow more and
compensate for the size difference acquired during division. This ensures that cell size is tightly regulated
and maintained within a physiologically viable range.