Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Simpler than expected: A microbial community with reduced diversity cleans up after algal blooms

29.07.2019

Algae blooms regularly make for pretty, swirly satellite photos of lakes and oceans. They also make the news occasionally for poisoning fish, people and other animals. What's less frequently discussed is the outsize role they play in global carbon cycling. A recent study now reveals surprising facts about carbon flow in phytoplankton blooms. Unexpectedly few bacterial clades with a restricted set of genes are responsible for a major part of the degradation of algal sugars.

Algae take up carbon dioxide (CO2) from the atmosphere and turn the carbon into biomass while releasing the oxygen back to the atmosphere. Fast algal growth during phytoplankton blooms leads to a massive transfer of carbon dioxide into algal biomass. But what happens to the carbon next?


Heligoland is Germany’s only true offshore island, famous for its seabirds, seals and duty-free shopping rather than for algae. The MPI-scientists studied the fate of the organic matter.

Max Planck Institute for Marine Microbiology, Naomi Esken

“Once the algae die, the carbon is remineralized by microorganisms consuming their biomass. It is thus returned to the atmosphere as carbon dioxide. Alternatively, if the dead algae sink to the seafloor, the organic matter is buried in the sediment, potentially for a very long time”, explains first author Karen Krüger from the Max Planck Institute for Marine Microbiology in Bremen. “The processes behind the remineralization of algal carbon are still not fully understood.”

Thus, Krüger and her colleagues investigated microorganisms during spring algal blooms in the southern North Sea, at the island of Heligoland. They specifically looked at the bacterial use of polysaccharides – sugars that make up a substantial fraction of the algal biomass. Together with colleagues from the Max Planck Institute, the University of Greifswald and the DOE Joint Genome Institute in California, Krüger carried out a targeted metagenomic analysis of the Bacteroidetes phylum of bacteria, since these are known to consume lots of polysaccharides.

In detail, the scientists looked at gene clusters called polysaccharide utilisation loci (PULs), which have been found to be specific to a particular polysaccharide substrate. If a bacterium contains a specific PUL, that indicates it feeds on the corresponding algal sugar.

Low PUL diversity

“Contrary to what we expected, the diversity of important PULs was relatively low”, says Krüger. Only five major polysaccharide classes were being regularly targeted by multiple species of bacteria, namely beta-glucans (such as laminarin, the main diatom storage compound), alpha-glucans (such as starch and glycogen, also algal and bacterial storage compounds), mannans and xylans (typically algal cell wall components), and alginates (mostly known as slimy stuff produced by brown macroalgae).

Of these five substrates, only two (alpha- and beta-glucans) make up the majority of substrates available to the bacteria during a phytoplankton bloom. This implies that the most important polysaccharide substrates released by dying algae are made up of a fairly small set of basic components.

“Given what we know of algal and bacterial species diversity, and the enormous potential complexity of polysaccharides, it came as no small surprise to see such a limited spectrum of PULs, and in only a relatively small number bacterial clades”, co-author Ben Francis from the Max Planck Institute for Marine Microbiology sums up in an accompanying comment.

“This was especially unexpected because previous studies suggested something different. An analysis of more than 50 bacterial isolates – i.e. bacteria that can be cultured in the lab – that our working group carried out in the same sampling region revealed a much broader diversity of PULs”, he adds.

Temporal succession of polysaccharide degradation

During the course of the algal bloom, the scientists observed a distinct pattern: In early bloom stages, fewer and simpler polysaccharides dominated, while more complex polysaccharides became available as the bloom progressed. This might be caused by two factors, Francis explains: “First, bacteria will in general prefer easily degradable substrates such as simple storage glycans over biochemically more demanding ones. Second, more complex polysaccharides become increasingly available over a blooms’ course, when more and more algae die.”

This study provides unprecedented insights into the dynamics of a phytoplankton bloom and its protagonists. A fundamental understanding of the bulk of glycan-mediated carbon flow during phytoplankton bloom events is now within reach. “Next, we want to dig deeper into processes underlying the observed dynamics”, says Krüger. “Moreover, it will be interesting to investigate polysaccharide degradation in habitats with other carbon sources, such as the Arctic Seas or the sediment.”

Wissenschaftliche Ansprechpartner:

Thomas Ben Francis
Max Planck Institute for Marine Microbiology, Bremen, Germany
Phone: +49 421 2028-545
E-Mail: tfrancis@mpi-bremen.de

Prof. Dr. Rudolf Amann
Max Planck Institute for Marine Microbiology, Bremen, Germany
Phone: +49 421 2028-930
E-Mail: ramann@mpi-bremen.de

Dr. Fanni Aspetsberger
Press Officer
Max Planck Institute for Marine Microbiology,
Bremen, Germany
Phone: +49 421 2028-947
E-Mail: faspetsb@mpi-bremen.de

Originalpublikation:

Karen Krüger, Meghan Chafee, T. Ben Francis, Tijana Glavina del Rio, Dörte Becher, Thomas Schweder, Rudolf I. Amann, Hanno Teeling: In marine Bacteroidetes the bulk of glycan degradation during algae blooms is mediated by few clades using a restricted set of genes. The ISME Journal. DOI: 10.1038/s41396-019-0476-y

Weitere Informationen:

https://www.mpi-bremen.de/en/Page3766.html
https://naturemicrobiologycommunity.nature.com/users/269126-ben-francis/posts/51...

Dr. Fanni Aspetsberger | Max-Planck-Institut für Marine Mikrobiologie

More articles from Life Sciences:

nachricht Blood and sweat: Wearable medical sensors will get major sensitivity boost
18.02.2020 | Moscow Institute of Physics and Technology

nachricht How to mend a broken heart
18.02.2020 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

Im Focus: New synthesis methods enhance 3D chemical space for drug discovery

After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.

"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.

Im Focus: Quantum fluctuations sustain the record superconductor

Superconductivity approaching room temperature may be possible in hydrogen-rich compounds at much lower pressures than previously expected

Reaching room-temperature superconductivity is one of the biggest dreams in physics. Its discovery would bring a technological revolution by providing...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

First research results on the "spectacular meteorite fall" of Flensburg

18.02.2020 | Earth Sciences

Blood and sweat: Wearable medical sensors will get major sensitivity boost

18.02.2020 | Life Sciences

How to mend a broken heart

18.02.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>