Light and electrons, Plasmodium wears green and gold

25 Mar 2010

Thursday 25 March

Speaker: Dr Eric Hanssen, Bio21 Institute Electron Microscopy Unit Manager and Research Fellow

Venue: Bio21 Institute Auditorium, 30 Flemington Road, Parkville

Time: 4.00 to 5.00pm

No RSVP required. All welcome.

Enquiries: Ross Campbell crc@unimelb.edu.au

Part of the Bio21 Institute Seminar Series

Abstract & bio:

Resolution …
The Holy Grail of biology would be the ability to image whole cells at high resolution, thus, localizing internal compartments and components to within a few nanometres. Usually, to obtain an image of a whole cell one has to compromise on the image resolution, as only part of the cell can be imaged if a resolution below the standard 250 nm of visible light is used. Electrons, X-rays and even visible light can be utilized, to some extent, to resolve these issues. While imaging with X-rays gives an intermediate resolution of about 50 nm, to achieve this with the other imaging modalities requires “cheating” with either image processing or sample preparation. For instance, the resolution achieved by light microscopy can be bettered by 2 to 3 fold using so called “super-resolution” microscopes, while the sample thickness observed in electron microscopy can be virtually unlimited using serial sections. Furthermore, all of these techniques can be used in a 3 dimensional mode to give a better understanding of the spatial arrangement of one’s sample.

We developed and applied these techniques to malaria, one of the major health problems in developing countries. The most severe and lethal form of this disease is caused by the apicomplexan parasite Plasmodium falciparum, which results in close to one million deaths per year. However, our knowledge about ability of the parasite to thrive within the host is limited. For instance, during intra-erythrocytic development the parasite reorganizes its host cell by exporting proteins beyond its own plasma membrane. As it is faced with a complete lack of endogenous protein trafficking machinery within the host red blood cell, it therefore has to export and install its own apparatus. In order to shed some light on the structure and organization of this system we have produced chimeric exported proteins whose GFP tags, coupled with super-resolution microscopy and 3D electron tomography, have enabled us to precisely locate them within different compartments of the exporting machinery. In the process, we have characterized new compartments in this well studied apparatus.

However, the resolution obtained with these techniques has made it clear that the transfection technology has some limits and dangers, which will be briefly discussed. Nevertheless, the application of tomography to the whole cell has enlightened the organisation of this system, as well as other mechanisms in Plasmodium. The equipment located in the EM unit at Bio21 was paramount to the success of this project and the possible applications of the different microscopes will be outlined during the talk.

Dr Eric Hanssen is a Research Fellow and Manager of the Electron Microscopy Unit at Bio21 Institute. Dr Hanssen is Internationally recognized in the field of extracellular matrix biology for developing advanced electron and atomic force microscopy techniques. Prior to his appointment, he has spent the last 4 years sharing his high-level imaging expertise at the ARC Centre of Excellence for Conherent X-ray Science (CXS) at La Trobe University. There he worked on developing new whole cell imaging techniques (e.g. Structural Illumination, Electron and X-ray tomography), using the Plasmodium malaria parasite as a model. He also has experience with whole tissue or cell culture.