Quantitative analysis of Plasmodium sporozoites structure and motility

by Kudryashev, Mikhail, PhD

Abstract (Summary)
In the current work I was studying motility and structure of the invasive stages of malaria parasites and bacteria causing Lyme disease with both light microscopy and cryo-electron tomography. For Plasmodium sporozoites I developed methodology and quantitative techniques to analyze live cell imaging data. This includes high content analysis of single sporozoite motility, high throughput analysis of hundreds of motile parasites and high throughput analysis of sporozoite transforming to the exoerythrocytic stages. The methodology allows quantitative analysis of sporozoite motility in different environments in vitro and in vivo and in silico simulating motility trajectories. Cryo-electron tomography allowed high resolution three dimensional observation of the whole natively preserved sporozoites. Microtubules in sporozoites have an additional density on the inner side of the wall potentially contributing to the stability and elasticity of the microtubules. The major organelles were found to be attached to the Inner Membrane Complex by elongated linker molecules. The Inner Membrane Complex had additional density at the cytoplasmic side potentially contributing to the sporozoite shape maintenance. Sporozoites showed three types of polarity: apical-posterior, dorso-ventral and concave-convex that have implications for directed motility of sporozoites. Cryo-electron tomography applied to four species of Borrelia causing different clinical symptoms revealed overall similar architecture and showed that B. garinii has significantly more periplasmic flagellar filaments. I could observe dividing bacteria and bacterial cytoskeleton – filaments similar to MreB and FtsZ. Closely associated bacteria were observed to fuse the outer membranes and in one case the cytoplasmic cylinders suggesting direct exchange of the genetic material. I performed computational averaging of over 100 individual flagellar motors from Borrelia revealing the resulting structure at 4.6 nm. This allowed visualizing the peptidoglycan
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Bibliographical Information:

Advisor:Freddy Frischknecht

School:Ruprecht-Karls-Universität Heidelberg

School Location:Germany

Source Type:Doctoral Dissertation

Keywords:malaria, motility, imaging, microscopy, cryo em, cryo electron tomography, borrelia


Date of Publication:07/23/2009

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