The viruses of the North Sea

Sep 13, 2021

Viruses in the ocean are numerous, diverse and play an important role in the marine carbon cycle.

A new study in ISME Journal provides exciting insights into the life of marine viruses in the North Sea during the spring bloom. Off the offshore island of Helgoland, researchers led by Nina Bartlau from the Max Planck Institute for Marine Microbiology found a dynamic viral community that can strongly influence the mortality of North Sea bacteria and thereby the carbon cycle of this habitat. They also discovered and isolated numerous new virus species.

Helgoland is Germany's only true offshore island, known more for seabirds, seals and duty-free shopping than for viruses. However, these were precisely the focus of the MPI researchers. (© Max Planck Institute for Marine Microbiology, Naomi Esken)

Bakteriophagen – also Viren, die Bakterien befallen – haben üblicherweise einen sogenannten Kopf und einen Schwanz, von dem wie Beinchen kleine Spikes abstehen. Die Viren namens Peternella auf diesem Bild aus dem Elektronenmikroskop sind etwa 150 nm lang, also etwa 500 mal kleiner als die Dicke eines menschlichen Haars. (© Georg Krohne)

Many new viruses discovered

The researchers found many new and very diverse phages in the North Sea. Phages are viruses that infect bacteria. Accordingly, the viruses studied here, which are specialized to infect Flavobacteria, are called flavophages. “The abundance and types of phages changed during the spring bloom. For example, at the beginning of the bloom we found only a few phages, which increased in abundance over time. We were also able to show that a particular phage species was only present for a short period of time, after which only its relatives remained,” explains co-author Cristina Moraru from the Institute of Chemistry and Biology of the Marine Environment (ICBM) at the University of Oldenburg. Over the years, however, the community of viruses was quite stable: Different phages could be found and isolated in two consecutive years.

Bartlau and her colleagues have thus collected numerous pieces of evidence that indicate: Viruses have a major impact on bacterial mortality during the spring bloom. The bacteria are responsible for breaking down the remains of microscopic algae over the course of the bloom, which largely releases the carbon dioxide absorbed by the algae from the atmosphere. “There is a possible link here between the viruses and the global carbon cycle, which will certainly be very exciting to investigate,” says Bartlau.

In der Überzahl: Die winzigen Viren drängen sich dicht um die ihre deutlich größeren Wirte, die Bakterien. Etwa 10 bis 45 Prozent der Bakterien im Meerwasser sind von Viren befallen. (© Georg Krohne)

Now also in the laboratory

The researchers also succeeded in cultivating numerous different and previously unknown viruses in the laboratory in Bremen. “We identified 10 new genera and also 10 new families,” says Bartlau. Many of them – 9 of the 10 genera and 4 of the 10 families to be exact – did not exist in culture before. “These new isolates now allow for exciting experiments in the lab to further our knowledge of flavophages and the role of viruses in the ocean,” Bartlau emphasizes. And this knowledge then goes far beyond the marine habitat, because some of the virus families isolated here also have members that live in freshwater, sewage and soil.

Original publication:

Nina Bartlau, Antje Wichels, Georg Krohne, Evelien M. Adriaenssens, Anneke Heins, Bernhard M. Fuchs, Rudolf Amann, Cristina Moraru (2021): Highly diverse flavobacterial phages isolated from North Sea spring blooms. ISME Journal.

DOI: 10.1038/s41396-021-01097-4

Participating institutions

Max Planck Institute for Marine Microbiology, Bremen
Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg
Imaging Core Facility, Biozentrum, University of Würzburg
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven
Quadram Institute Bioscience, Norwich Research Park, Norwich, UK