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 First SARS-CoV-2 genomes in Austria openly available
03.04.2020 | CeMM Forschungszentrum für Molekulare Medizin der Österreichischen Akademie der Wissenschaften

nachricht Do urban fish exhibit impaired sleep? Light pollution suppresses melatonin production in European perch
03.04.2020 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Harnessing the rain for hydrovoltaics

Drops of water falling on or sliding over surfaces may leave behind traces of electrical charge, causing the drops to charge themselves. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz have now begun a detailed investigation into this phenomenon that accompanies us in every-day life. They developed a method to quantify the charge generation and additionally created a theoretical model to aid understanding. According to the scientists, the observed effect could be a source of generated power and an important building block for understanding frictional electricity.

Water drops sliding over non-conducting surfaces can be found everywhere in our lives: From the dripping of a coffee machine, to a rinse in the shower, to an...

Im Focus: A sensational discovery: Traces of rainforests in West Antarctica

90 million-year-old forest soil provides unexpected evidence for exceptionally warm climate near the South Pole in the Cretaceous

An international team of researchers led by geoscientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have now...

Im Focus: Blocking the Iron Transport Could Stop Tuberculosis

The bacteria that cause tuberculosis need iron to survive. Researchers at the University of Zurich have now solved the first detailed structure of the transport protein responsible for the iron supply. When the iron transport into the bacteria is inhibited, the pathogen can no longer grow. This opens novel ways to develop targeted tuberculosis drugs.

One of the most devastating pathogens that lives inside human cells is Mycobacterium tuberculosis, the bacillus that causes tuberculosis. According to the...

Im Focus: Physicist from Hannover Develops New Photon Source for Tap-proof Communication

An international team with the participation of Prof. Dr. Michael Kues from the Cluster of Excellence PhoenixD at Leibniz University Hannover has developed a new method for generating quantum-entangled photons in a spectral range of light that was previously inaccessible. The discovery can make the encryption of satellite-based communications much more secure in the future.

A 15-member research team from the UK, Germany and Japan has developed a new method for generating and detecting quantum-entangled photons at a wavelength of...

Im Focus: Junior scientists at the University of Rostock invent a funnel for light

Together with their colleagues from the University of Würzburg, physicists from the group of Professor Alexander Szameit at the University of Rostock have devised a “funnel” for photons. Their discovery was recently published in the renowned journal Science and holds great promise for novel ultra-sensitive detectors as well as innovative applications in telecommunications and information processing.

The quantum-optical properties of light and its interaction with matter has fascinated the Rostock professor Alexander Szameit since College.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

13th AKL – International Laser Technology Congress: May 4–6, 2022 in Aachen – Laser Technology Live already this year!

02.04.2020 | Event News

“4th Hybrid Materials and Structures 2020” takes place over the internet

26.03.2020 | Event News

Most significant international Learning Analytics conference will take place – fully online

23.03.2020 | Event News

 
Latest News

Capturing 3D microstructures in real time

03.04.2020 | Materials Sciences

First SARS-CoV-2 genomes in Austria openly available

03.04.2020 | Life Sciences

Do urban fish exhibit impaired sleep? Light pollution suppresses melatonin production in European perch

03.04.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>