Towards Single Cell Optical Tomography

Abstract

Using a single-beam, oscillating Optical Tweezers we demonstrate trapping and rotation of rod-shaped bacterial cells with respect to the optical axis [1]. The angle of rotation is determined by the amplitude of the oscillation. This technique allows imaging fluorescently labeled 3D sub-cellular structures from different, optimized viewpoints. To illustrate our method we analyze the Z-ring of E. coli [2]. We use cells that express FtsZ-GFP and have their cytoplasmic membrane stained with FM4-64 (Figure). In a vertically oriented cell, both the Z-ring and the cytoplasmic membrane images appear as symmetric circular structures that lend themselves to quantitative analysis.Scanning the cell alignment and using 3D image reconstruction from the corresponding images of a fluorescently labeled 3D sub-cellular structure, would make our approach analogous to that of cryo-electron tomography.Figure - A trapped E. coli cell. Left: horizontal orientation; Right: vertical orientation. A) Phase contrast image, B) FM4-64 image of the cytoplasmic membrane, C) GFP image of the Z-ring.View Large Image | View Hi-Res Image | Download PowerPoint Slide