Nav: Home

Viruses as modulators of interactions in marine ecosystems

September 26, 2019

The Oceans not only host large predators such as sharks or orcas. Even in the realm of the microscopic some unicellular species consume others. Choanoflagellates belong to these unicellular predators. They are widespread in the ocean and eat bacteria and small algae. Choanoflagellates are considered among the closest living unicellular relatives of animals and can transition to a multicellular state. For that reason they are often studied for understanding how multicellular organisms like us came to be.

Now, a team of scientists led by Professor Alexandra Z. Worden (GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany/Monterey Bay Aquarium Research Institute, MBARI, USA) has provided the first insights in the interaction between choanoflagellates and viruses. In a multi-year intensive effort the team was able to detect the genome of a giant virus in these unicellular predators. The virus had a genome size and gene numbers comparable to small bacteria. More surprising than the genome size were the many functions it encodes and brings to the host. The study has just been published in the international journal Proceedings of the National Academy of Sciences USA.

For the study the scientists repeatedly went to sea with high-tech instrumentation and the goal to look at all the predatory unicellular organisms in the water using a laser-based visualization system. Then they individually separated these cells from other microbes in a process called single-cell sorting. "Each individual predator from the wild was then sequenced - and the single-cell sorts from one Pacific Ocean sample were dominated by an uncultured species of choanoflagellate", Professor Worden explains.

In the same cells Dr. David Needham, a postdoctoral researcher in the Worden Lab and co-first author of the report, found the genome sequence of a virus. He showed that remarkably the virus encodes genes for microbial rhodopsin proteins and associated pigments, a suite of genes not seen together before in a virus. Other types of rhodopsin systems are known for being responsible for the detection of light in the eyes of vertebrates and many other animals.

While the GEOMAR/MBARI team and collaborators from the US, Canada and UK focused on the genome-based discoveries alongside the evolutionary biology and distribution of the virus, a collaborating team located at the University of Tokyo, RIKEN Center for Biosystems Dynamics Research and other Japanese Institutions led studies that generated the crystal structure of the protein and demonstrated that it acts as a light driven proton pump.

"Taken together, this means that the host, which is a predatory consumer just like many animals, uses sunlight when infected by the virus", stresses Professor Worden. The researchers also broadened knowledge on the distribution of these genes in giant viruses in the oceans - and showed that the rhodopsin proteins likely have many specialized roles in eukaryotic cells - both phytoplankton and unicellular predators. Yet to be elucidated is the exact role of the virus in the host cell. "Is it for energy transfer? Or a new light sensing capability perhaps driving motility or other behaviours?", Prof. Worden summarizes these as being important open questions.

The study by Worden's team and collaborators is one of two reports by GEOMAR scientists just published on the role of viruses in marine ecosystems. In another remarkable study employing a suite of innovative methods in the framework of the Collaborative Research Centre 1182 "Metaorganisms" Professor Ute Hentschel Humeida's research group published the results showing the complicated relationship between bacteria, viruses infecting bacteria (bacteriophages), and marine sponges. They discovered that even neighbouring sponge animals, although massively filtering the same seawater to capture food particles, host individually unique and species-specific viral communities. "Each sponge individual has its own unique virome that is distinct from that of the neighbouring sponges", says first author Martin T. Jahn. One abundant group of bacteriophages in sponges endows symbiotic bacteria with proteins enabling bacteria to escape immune responses of the host sponge. These particular bacteriophages are found to be widespread in diverse host-associated environments, including human.

"Together, these two studies show that we have only started to understand the role of viruses in marine ecosystems, but also for life on earth in general. Research on marine viral diversity - and its functional meaning for ecosystem processes are just at the beginning", Prof. Hentschel Humeida of GEOMAR summarizes. "The power of these two studies" emphasizes Prof. Worden "is that they have elucidated major new features of host-virus interactions in the wild - bringing state-of-the-art technologies and methodologies to the field to study uncultured but widespread marine organisms. This opens new doors for understanding marine communities, how they interact and are how they are regulated - factors that are of upmost importance as we try to understand how communities will change in the future."
-end-


Helmholtz Centre for Ocean Research Kiel (GEOMAR)

Related Bacteria Articles:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.
How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.
Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.
Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.
Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.
Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.
Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.
How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.
The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?
Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.
More Bacteria News and Bacteria Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Debbie Millman: Designing Our Lives
From prehistoric cave art to today's social media feeds, to design is to be human. This hour, designer Debbie Millman guides us through a world made and remade–and helps us design our own paths.
Now Playing: Science for the People

#574 State of the Heart
This week we focus on heart disease, heart failure, what blood pressure is and why it's bad when it's high. Host Rachelle Saunders talks with physician, clinical researcher, and writer Haider Warraich about his book "State of the Heart: Exploring the History, Science, and Future of Cardiac Disease" and the ails of our hearts.
Now Playing: Radiolab

Insomnia Line
Coronasomnia is a not-so-surprising side-effect of the global pandemic. More and more of us are having trouble falling asleep. We wanted to find a way to get inside that nighttime world, to see why people are awake and what they are thinking about. So what'd Radiolab decide to do?  Open up the phone lines and talk to you. We created an insomnia hotline and on this week's experimental episode, we stayed up all night, taking hundreds of calls, spilling secrets, and at long last, watching the sunrise peek through.   This episode was produced by Lulu Miller with Rachael Cusick, Tracie Hunte, Tobin Low, Sarah Qari, Molly Webster, Pat Walters, Shima Oliaee, and Jonny Moens. Want more Radiolab in your life? Sign up for our newsletter! We share our latest favorites: articles, tv shows, funny Youtube videos, chocolate chip cookie recipes, and more. Support Radiolab by becoming a member today at Radiolab.org/donate.