Biophysics and Biophotonics group

We develop experimental tools such as optical tweezers for single cell manipulation, optical tweezers for single macro-molecule force spectroscopy, and Laser Tweezers Raman Spectroscopy. In addition, we develop and apply digital holographic microscopy techniques, microfluidic devices, image-processing algorithms, and high-speed imaging techniques. To better understand the system under study we also develop theoretical physical models that are solved using numerical methods.

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Infection biology research

The group is running two projects aimed at investigating how bacteria attach to surfaces with pili and how bacterial spores can resist heat, radiation and chemicals.

How do bacteria attach to surfaces?

Multi-resistant bacterial infections are increasing at an alarming rate in both developing and industrialised countries. We must therefore immediately tackle the problem of multi-resistance and develop new effective methods, substances and materials that can disarm and prevent bacteria from causing infections. However, to achieve this, we need to increase our knowledge of the infection process and identify which parts we should attack. Because bacteria must first attach to host cells to create an infection, one of the strategies is to reduce the bacteria’s ability to attach. Therefore, we need to better understand how bacteria manage to attach and stay in their natural environment.

We focus on mapping the attachment mechanism of bacteria. Primarily, we are striving to understand how pathogenic Escherichia coli bacteria manage to attach to host cells in different environments, such as in the intestines or urinary tract. For example, it has been shown that in order to be able to infect a host cell, bacteria have developed effective and unique ways of adapting to their environment. The digestive system, especially the intestines, is an environment that is often affected by pathogenic bacteria. For example, the enterotoxic bacterium Escherichia coli (ETEC) causes severe diarrhoea, a disease that affects more than 200 million people per year of which around 2 million die. Most of these people live in developing countries.

In the intestine, ETEC bacteria attach to microvilli, which are short protrusions on the tissue, and there the ETEC are exposed to powerful flows of fluid generated by the peristaltic movement of the intestines. These flows cause high shear forces which bacteria must resist in order not to be flushed away. To survive in such a harsh environment, ETEC bacteria develop 1-2 micrometre long threads on their surface, known as fimbriae, which can attach to the host's tissue. We characterise the biomechanical properties of these fimbriae by using force-measuring optical tweezers. With optical tweezers, we can measure forces that are lower than 10^ -12 N (i.e. pN).

In recent years, we have successfully investigated the mechanics of fimbriae from bacteria that cause diarrhoeal diseases, urinary tract infections, and which attach to materials in a hospital environment. We thereby now have a good understanding of how they help the bacteria to attach to surfaces. Although we have managed to characterise most fimbriae, many questions remain about how bacteria cling on to surfaces with the help of these “arm-like” structures and what role they play when there is infection.

How can bacterial spores be so resistant to heat and chemicals?

Spore-forming bacteria that cause diseases, destroy food and cause food poisoning pose a danger and burden society with enormous costs. The spores are also highly resistant to heat, radiation and chemicals, which makes them very difficult to kill. The resilience, robustness and disease-causing ability of spores are therefore a challenge, for example, for healthcare and the food industry, and also make it possible for them to be used as biological weapons.

To deal with these challenges, it is important we understand the structure of the spores and that there are reliable decontamination and indication methods. Through this interdisciplinary project, we intend to answer the following research questions:

• What are the processes of biochemical and morphological changes when bacterial spores develop?

• How do various killing agents affect the life cycle of the bacterium and what is the most effective way of killing spores?

• How can spores be indicated without coming in contact with them and how can pathogenic spores be removed from their natural background?

The results from these studies will give us an increased understanding of the bacteria's life cycle and the time scale of the molecular processes that occur in spores during development and when they after exposure to different killing methods, for example, those involving chemicals, radiation or heat. This knowledge will increase our insight into the robustness of the spores and how they can be detected, as well as insight into mechanisms at molecular level. This will thereby give us ideas for new strategies for controlling pathogenic spore-forming bacteria.