First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Karel Mocaer is first author on ‘ Targeted volume correlative light and electron microscopy of an environmental marine microorganism’, published in JCS. Karel is a PhD student in the lab of Yannick Schwab at EMBL, Heidelberg, Germany, where she is interested in ultrastructural studies of marine microorganisms using various electron microscopy techniques.

Karel Mocaer

How would you explain the main findings of your paper in lay terms?

Our article offers a new approach to studying marine microorganisms directly collected from their natural environment. Small planktonic cells are ecologically important as they are part of the marine food web, and some can produce O2 through photosynthesis. Until now, our knowledge was still mostly limited to cells that can be maintained in the laboratory, which represents only a small fraction of these types of organism. Our culture-free approach, allowing the 3D visualization of the inner machinery of wild plankton, could ultimately help better understand how they function.

Were there any specific challenges associated with this project? If so, how did you overcome them?

Initially, I was not a field scientist. Thus, learning how to logistically plan sampling expeditions as well as how to collect samples on site was a challenge. The help from the team of Johan Decelle, who has a lot of field experience, was very valuable for me to learn how to collect marine organisms at sea. Moreover, teaming up with Anna Steyer to efficiently process the samples on site was very important.

When doing the research, did you have a particular result or ‘eureka’ moment that has stuck with you?

One particular moment that stuck with me is when the segmentation of the outer layer of the cell (theca) appeared. Seeing that we could achieve this level of detail from our volume electron microscopy (vEM) dataset was very exciting, as it allowed for taxonomical identification at the species level.

Why did you choose Journal of Cell Science for your paper?

We felt that the Journal of Cell Science was a good match scientifically for our research article. Additionally, we highly appreciated the open access options as well as the involvement of the Company of Biologists in biodiversity initiatives.

Scanning electron microscopy micrograph of a marine dinoflagellate cell.

Scanning electron microscopy micrograph of a marine dinoflagellate cell.

Have you had any significant mentors who have helped you beyond supervision in the lab? How was their guidance special?

My supervisor, Yannick Schwab, has been a very important mentor to me. I'm very thankful for the scientific supervision but also for all the support during COVID-19 times as well as for the help to overcome stage fright while presenting. I would also like to deeply acknowledge Paolo Ronchi and Viola Oorschot, members of the EMCF at EMBL, whose expertise is incomparable and who have encouraged and supported me profoundly on a daily basis. I would like to thank our laboratory manager, Inés Romero Brey for her assistance and contagious enthusiasm. Finally, two more significant mentors would be my former French supervisors Romain Gibeaux and Denis Chrétien, who from my first day of internship were discussing carrier developments as well as science in broader terms.

What motivated you to pursue a career in science, and what have been the most interesting moments on the path that led you to where you are now?

There have been many moments that led to where I am now in science. One significant moment was during my first internship, with Marc-Étienne Huot and Suryasree Subramania, where I discovered my passion for research. During my Master's program (BMC) in Rennes, I had incredible teachers who provided great scientific training. At that time, a visit to a cryo-electron microscopy laboratory captivated me. I won't ever forget the first time I saw an electron microscope. Soon after, I had the chance to perform an internship with this group, with Denis Chrétien and Romain Gibeaux, who have been truly amazing mentors. During my time in their lab, I saw a spectacular talk by Yannick Schwab, which fully motivated my application to EMBL to pursue a PhD. Yannick, his group and the EM facility team have been a daily motivation and inspiration ever since I joined them for my PhD.

Who are your role models in science? Why?

Science is full of inspiring people. One of my role models is Rachel Carson, a dedicated marine biologist who was passionate about nature and fought to protect the environment. From more recent years, I was truly inspired by the science of Gaia Pigino and her team, tackling scientific questions with an elegant panel of complementing methods.

What's next for you?

I'm very interested to pursue academia and hope to continue after my PhD with a post-doctoral position using electron microscopy techniques.

Tell us something interesting about yourself that wouldn't be on your CV

My family is originally from a small island at the edge of Brittany called Ouessant. This is where my love for the sea emerged from a very young age. Coming from a long line of sailors, I did not think that science would eventually bring me back on a boat.

Karel Mocaer’s contact details: EMBL, Meyerhofstraße 1, 69117 Heidelberg, Germany.

E-mail: karel.mocaer@embl.de

Mocaer
,
K.
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Mizzon
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G.
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Gunkel
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M.
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Halavatyi
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A.
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Steyer
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A.
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Oorschot
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V.
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Schorb
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M.
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Le Kieffre
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C.
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Yee
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D. P.
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Chevalier
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et al. 
(
2023
).
Targeted volume correlative light and electron microscopy of an environmental marine microorganism
.
J. Cell Sci.
136
,
jcs261355
.