Probe Pattern Transitions in Bacterial Oscillating System using Palm Imaging and Nanofluidic Confinement

Abstract

Faithful cell division of bacterium E. coli relies on remarkable oscillations of the MinCDE system to perform accurate and symmetric septation. Perturbing this bio-oscillator by disrupting minB locus or altering MinDE expressions is known to cause mini-celling and otherwise filamentous phenotypes. Recent reports suggested MinE plays a pivotal role in spatiotemporal pattern formation of MinDE cohorts; yet it remains elusive if their pattern transitions led to changes in cell morphology, and vice versa.In the present study, the coupling dynamics of MinDE interplays is investigated by time-lapse microscopy. We used multicolor fluorescence imaging to detail the mode transitions in distinct MinDE pattern formations, and photoactivated localization microscopy (PALM) to probe the nanoscale fine structures of the MinDE filaments/patterns in living cells. Despite E-ring capping has been viewed as a drive of pole-to-pole MinD oscillations, we found peculiar expression signatures in MinD and MinE spatiotemporal distributions, corresponding to MinDE patterns other than the E-ring type, correlate to their relative expression levels. Alternatively, bacteria were cultured and confined in micro/nanofluidic devices, to mimic various curvature changes of cell peripherals. Interestingly, under strong nanoslit confinement of 400 nm depth, bacteria are able to proliferate, but show irregular pancake-like morphology and intermittent oscillation episodes were observed in MinDE dynamics. The transitions between intermittent episodes display period-doubling signature of bifurcation by analyzing image series via spatial time-frequency method.Our results indicate MinDE pattern fluctuations / transitions correspond to aberrancy in septation and morphology. The study synergizes the join merits of in vivo imaging, single cell analysis, and nanofluidics to grasp the insight of noisedriven pattern transitions and phenotypic changes in bacteria.