Adaptation to stress at cellular level

Nutrients are building blocks for cell components, but also serve as signalling elements that control basic cellular functions. Cells must cope with different kinds of stress, such as fluctuations in osmolytes, oxygen levels or pH, and their adaptation requires a coordinated response from various cellular pathways. Svenja has concentrated on osmotic stress to sodium chloride and lithium chloride in the microorganism Saccharomyces cerevisiae, commonly known as baker’s yeast.

– We have added these salts, sodium chloride and lithium chloride, to the cell medium and studied the stress response to that. We were interested in how cells adapt and how they make use of carbon sources for example if they are missing proteins that normally regulate stress responses or nutrient signalling. Lithium chloride is a bit different if compared to other salts such as sodium chloride. It targets various enzymes that are not necessarily related in the function they exert within yeast cells. As such it is difficult to exactly find out which cellular processes lie behind the adaptation to this salt. We found hints that this adaptation might include regulators that are specifically involved in the cell’s response to glucose and hence are interested in this cross section.

The handy organism yeast

As said, Svenja uses baker’s yeast as a model organism. It is a single cell organism that is easy to handle and happy in simple conditions where it can grow quite fast, and its genome is easy to modify. Although baker’s yeast is different from higher organisms like animals or humans in many obvious ways, they share several traits. Yeast cells are organised very similar to cells in higher organisms and about a third of the genes found in baker’s yeast are similar to human genes. For first line research as Svenja’s, it is therefore useful to obtain information about basic biological processes, even those that can be of relevance in human diseases.

However, Svenja is careful to point out that her findings cannot be directly translated to other cells as those in mammals. The purpose is rather to give a basic understanding of the processes, to find out what mechanisms are important and what paths that seem to be worth exploring further. The work has made progress in observing different relevant regulators and the process in which they affect the connection between lithium chloride and glucose signalling in the cells. These findings contribute to the understanding of the complex crosstalk between nutrient signalling and osmotic stress responses, even if there are yet no definitive results, as so often in fundamental research.

Several expertises needed

Svenja began her PhD in natural science from the biologist point of view, but now considers herself to be somewhere in the middle of biology and bioinformatics. She earlier worked as a nurse and the many elderly patients made her curious of the processes in ageing and how individuals are affected so differently by age-related diseases, and wanted to know more. She notes that the processes she has looked into would have been hard to solve solely with methods of classic molecular biology. In the systems biology research group led by Svenja’s supervisor Marija Cvijovic people have different expertises that are used together.

– During my PhD years, I have learnt a lot more than the topic at hand: as a laboratory biologist I have learnt patience and tolerance and to find solutions to things that happen unexpectedly. Yeast is after all an organism, and sometime behaves in unexpected ways. As a member in an interdisciplinary research group I have learnt to communicate my research clearly and understandably, and take on the perspective of researchers from various other disciplines.

After the exam, Svenja wants to relax for a while, maybe travel and catch up with friends. In the future she finds it would be interesting to transition into translational medicine, to use all her three expert areas of biology, medicine and bioinformatics. Maybe, she could continue to work with nutrient signalling.

Svenja Braam will defend her PhD thesis Yeast at the Crossroads: Nutrient Signalling Paths and Stressful Turns on November 29 at 9.00 in the lecture hall Pascal, Hörsalsvägen 1. Supervisor is Marija Cvijovic, assistant supervisor is Niek Welkenhuysen.