Biophysical Society Thematic Meeting - June 28-July 1, 2015

New Biological Frontiers Illuminated by Molecular Sensors and Actuators

Wednesday Speaker Abstracts

Observing the Helicase Activity of Ribosome 30S during Translation Initiation by Using Optical Tweezers Yi-Lan Chen 1 , Jin-Der Wen 2 . 1 Genome and Systems Biology Program, National Taiwan University, Taipei, Taiwan, 2 Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan. See abstract: Pos-6 Board 6

Nanofabrication as a Tool to Study the Effects of Cell Shape on Chromosome and Protein Organization in Bacteria Cees Dekker . Kavli Institute NanoScience Delft, Delft, Netherlands. The general principles underlying the interplay between intracellular molecular networks and the cell boundary are essential to cell biology, yet largely unexplored. Here, we use nanofabricated chambers to ‘sculpt’ living bacterial cells into defined shapes that deviate from their natural phenotype, and subsequently we study the organization of proteins and DNA in these shape sculptures. I will show our ability to shape live E. coli bacteria into novel shapes such as rectangles, squares, triangles and circles. We use these to explore the spatial adaptation of Min proteins that oscillate pole-to-pole in rod-shape Escherichia coli to assist cell division. In a wide geometric parameter space from 2x1x1 to 11x6x1 μm3, Min proteins exhibit versatile oscillation patterns, sustaining rotational, longitudinal, diagonal, stripe, and even transversal modes. These patterns are found to directly capture the symmetry and scale of the cell boundary, and the Min concentration gradients scale in adaptation to the cell size within a characteristic length range of 3–6 μm. Numerical simulations reveal that local microscopic Turing kinetics of Min proteins can yield global symmetry selection and gradient scaling, when and only when facilitated by the three- dimensional confinement of cell boundary. These findings contrast previous geometry-sensing models based on the longest distance, membrane area or curvature, and reveal that spatial boundaries can facilitate simple molecular interactions to result in far more versatile functions than previously understood. Furthermore I will show preliminary data on the organization of (single) chromosomes in shaped cells that illustrate how DNA is organized in an expanded cytosolic volume. Finally, I will briefly sketch some of our ideas to explore the building of synthetic cells, specifically our first steps to establish synthetic cell division.

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