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NGL lecture: Zooming in on bacterial behaviour

Thursday 19 April 2018
Niels Bohrweg 2
2333 CA Leiden

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Microbes are the most abundant organisms on earth and impact all aspects of our lives. But their small size makes them difficult to study, and we are just beginning to understand their cellular structure and how they utilize molecular machines for their complex behaviours.  

Many bacteria are motile – they either swim or crawl on surfaces by specialized cell appendages. But these movements are not random, they are directed by a sensory apparatus called the chemoreceptor array. This ‘bacterial nose’ allows the cells to 'smell' their chemical environment and enables them to seek out their most favourable conditions. Several microbes that cause diseases utilize this system as the first step of host invasion.

In order to gain insight into the structure and function of the molecular machines involved in this behaviour, we use a method called electron cryotomography. This allows the study of molecular machines in three dimensions and at macromolecular resolution in intact cells.

About Ariane Briegel

Freezing bacteria super fast to gain a true-to-nature image of the internal and external structure. Ariane Briegel ,professor of Ultrastructural Biology, came specially to Leiden to carry out this research. Leiden University is one of the few institutes in the world to have the necessary equipment.

Briegel works mainly with highly advanced cryo-electron tomography, to image bacteria that are normally too small to see. 'We freeze the bacteria super fast – a true flash-freeze – so that the specimen is contained in perfectly clear ice.’ It's so fast that the water in the cell has no time to crystallise. 'The bacteria remains completely intact and there are no defects in the image.'

The specimen is then placed under an advanced electron microscope, where it is spun round. The resulting 2D recordings are combined to create a 3D image, comparable to hospital CT-scanners. The combination of these techniques offers a completely new vision of the world of microbes. ‘Cryo-electron tomography is the first technique for looking at bacteria in their natural state, exactly how they normally look.' This technique is necessary to answer for example how bacteria move, and which signals trigger that movement. It is a small step from studying bacterial movement to prevention of infections, and their spreading.

The Natuurwetenschappelijk Gezelschap Leiden organises lectures in Dutch and English for everyone who is interested in science.

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