ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology during our centenary year but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Jennifer Steffen is an author on ‘ Combined effects of salinity and intermittent hypoxia on mitochondrial capacity and reactive oxygen species efflux in the Pacific oyster, Crassostrea gigas’, published in JEB. Jennifer is a PhD candidate in the lab of Prof. Dr Inna Sokolova at the Institute of Biological Sciences, University of Rostock, Germany, investigating biochemical and molecular physiological adaptations to environmental changes with a special emphasis on mitochondrial functions.

Jennifer Steffen

Describe your scientific journey and your current research focus

My fascination for marine biology brought me to my bachelor's degree in biology, where I gained a lot of experience in marine ecology research as a student assistant early on. To deepen my knowledge, I went to Victoria University Wellington in New Zealand for 6 months, where I learned a lot about cnidarian–dinoflagellate symbiosis and confocal microscopy. I then specialised in marine biology for my master's degree, where I discovered my interest in integrative ecophysiology. Focusing on molecular biomarkers in polar cod in response to global warming and acidification, I found my passion specifically in biochemical and molecular studies. My current PhD thesis now allows me to investigate biochemical and molecular mechanisms of hypoxia tolerance in marine bivalves. The mitochondrial research has fascinated me the most, which I would very much like to continue.

How would you explain the main finding of your paper to a member of the public?

Oxygen is vital to most organisms in this world. This is because oxygen is needed by the cell to provide energy for all body functions. Mitochondria are the so-called powerhouses of the cell. Here, ATP is produced in a complex chain of reactions involving various enzymes, which need oxygen. If there is a lack of oxygen, these reactions can no longer take place, energy is no longer produced and cell damage occurs. This is the case with strokes or heart attacks, in which tissue is no longer supplied with blood and thus receives no oxygen. Now look at the Pacific oyster, which everyday experiences low and high tides and survives long periods without oxygen. There are many adaptations to such environmental conditions. However, I am interested in adaptations and tolerance mechanisms relating to the mitochondria because they are the first to be affected when oxygen is depleted. Therefore, I exposed Pacific oysters to oxygen deficiency and additionally to further stress from different sea water salinity. My results showed that oyster mitochondria did not exhibit severe damage or dysfunction during oxygen depletion. Oysters that had been acclimated to low salinity showed generally better mitochondrial performance, which may show that low salinity is closer to optimal living conditions for oysters. However, the better performance at low salinity was found to be associated with a cost in the form of damaging by-products. This robust mitochondrial tolerance of salt and also oxygen deficiency might be part of the Pacific oyster's successful invasion of European waters.

Which part of this research project was the most rewarding/challenging?

The most challenging part of this project was understanding the complexity of mitochondrial functions. After measurement, you have this large dataset and although it is known which mitochondrial function is manipulated during each step of SUIT (substrate–uncoupler–inhibitor titration protocol, which is the basis of every measurement via high-resolution respirometry), the difficulty is in bringing the results into the context of the complex mitochondrial system. However, I can recall this rewarding moment, when I completed my measurements. In theory, you only must isolate mitochondria, put them into the oxygraph and start to titrate different substrates to stimulate or inhibit certain respiratory complexes. However, mitochondrial isolations do not always work and it took me almost 2 months to obtain a sufficient sample size; my supervisor always told me when working with mitochondria you develop a high frustration tolerance.

The little ‘goblin’ used to investigate mitochondrial functions: the oxygraph.

The little ‘goblin’ used to investigate mitochondrial functions: the oxygraph.

What do you think experimental biology will look like 50 years from now?

Experimental biology in 50 years from now will use more non-invasive methods. Looking at the developmental speed of new technologies, possibilities of non-invasive methods will grow. Additionally, integration of different methods and natural conditions might become easier with improved computational assistance.

If you had unlimited funding, what question in your research field would you most like to address?

With unlimited funding, I would like to compare mitochondrial functions of as many bivalve species from different habitats and lifestyles as possible and how these mitochondrial responses to hypoxia are integrated in whole-organism responses by measuring with the non-invasive MRI method. In addition, it would be interesting to do time series studies to see long-term effects of hypoxia by using more natural conditions or even field experimental set ups.

What changes do you think could improve the lives of early-career researchers, and what would make you want to continue in a research career?

Nowadays, research of new topics requires much better and usually more expensive methods to re-explore facts based on old knowledge or to understand a given topic even deeper/more precisely. I think many young researchers would say the same here: improve the funding to allow one to do research but also to have enough for living. Also, I would like to see young researchers not having to choose between family and career. Especially today, there should be better possibilities to combine both, particularly at early career stages where the issue is usually more relevant. I would very much like to continue my research and I am curious where I will end up in the world as a PostDoc, but I know the problem, especially here in Germany, that there are hardly any opportunities to find jobs after the PostDoc period. I would wish for more possibilities to stay in academia after early career stages.

Jennifer Steffen's contact details: Department of Marine Biology, Institute of Biological Sciences, University of Rostock, 18051 Rostock, Germany.

E-mail: [email protected]

J. B. M.
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Combined effects of salinity and intermittent hypoxia on mitochondrial capacity and reactive oxygen species efflux in the Pacific oyster, Crassostrea gigas
J. Exp. Biol.