Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Flowing electrons help ocean microbes gulp methane

21.09.2015

Good communication is crucial to any relationship, especially when partners are separated by distance. This also holds true for microbes in the deep sea that need to work together to consume large amounts of methane released from vents on the ocean floor. Recent work at Caltech has shown that these microbial partners can still accomplish this task, even when not in direct contact with one another, by using electrons to share energy over long distances.

This is the first time that direct interspecies electron transport--the movement of electrons from a cell, through the external environment, to another cell type--has been documented in microorganisms in nature.


Pictured is a high magnification image of sediment enriched in syntrophic consortia. In the center of the image is an overview of sediment containing cells, and individual -- roughly spherical -- microbial communities are shown at high magnification at the ends of lines extending from the center. Fluorescent signals show the ANME-2c archaeal subgroup in red, and sulfate reducing bacteria are shown in green. Sediment particles appear yellow.

Credit: Grayson Chadwick/Caltech

The results were published in the September 16 issue of the journal Nature.

"Our lab is interested in microbial communities in the environment and, specifically, the symbiosis--or mutually beneficial relationship--between microorganisms that allows them to catalyze reactions they wouldn't be able to do on their own," says Professor of Geobiology Victoria Orphan, who led the recent study.

For the last two decades, Orphan's lab has focused on the relationship between a species of bacteria and a species of archaea that live in symbiotic aggregates, or consortia, within deep-sea methane seeps. The organisms work together in syntrophy (which means "feeding together") to consume up to 80 percent of methane emitted from the ocean floor--methane that might otherwise end up contributing to climate change as a greenhouse gas in our atmosphere.

Previously, Orphan and her colleagues contributed to the discovery of this microbial symbiosis, a cooperative partnership between methane-oxidizing archaea called anaerobic methanotrophs (or "methane eaters") and a sulfate-reducing bacterium (organisms that can "breathe" sulfate instead of oxygen) that allows these organisms to consume methane using sulfate from seawater. However, it was unclear how these cells share energy and interact within the symbiosis to perform this task.

Because these microorganisms grow slowly (reproducing only four times per year) and live in close contact with each other, it has been difficult for researchers to isolate them from the environment to grow them in the lab. So, the Caltech team used a research submersible, called Alvin, to collect samples containing the methane-oxidizing microbial consortia from deep-ocean methane seep sediments and then brought them back to the laboratory for analysis.

The researchers used different fluorescent DNA stains to mark the two types of microbes and view their spatial orientation in consortia. In some consortia, Orphan and her colleagues found the bacterial and archaeal cells were well mixed, while in other consortia, cells of the same type were clustered into separate areas.

Orphan and her team wondered if the variation in the spatial organization of the bacteria and archaea within these consortia influenced their cellular activity and their ability to cooperatively consume methane. To find out, they applied a stable isotope "tracer" to evaluate the metabolic activity. The amount of the isotope taken up by individual archaeal and bacterial cells within their microbial "neighborhoods" in each consortia was then measured with a high-resolution instrument called nanoscale secondary ion mass spectrometry (nanoSIMS) at Caltech. This allowed the researchers to determine how active the archaeal and bacterial partners were relative to their distance to one another.

To their surprise, the researchers found that the spatial arrangement of the cells in consortia had no influence on their activity. "Since this is a syntrophic relationship, we would have thought the cells at the interface--where the bacteria are directly contacting the archaea--would be more active, but we don't really see an obvious trend. What is really notable is that there are cells that are many cell lengths away from their nearest partner that are still active," Orphan says.

To find out how the bacteria and archaea were partnering, co-first authors Grayson Chadwick (BS '11), a graduate student in geobiology at Caltech and a former undergraduate researcher in Orphan's lab, and Shawn McGlynn, a former postdoctoral scholar, employed spatial statistics to look for patterns in cellular activity for multiple consortia with different cell arrangements. They found that populations of syntrophic archaea and bacteria in consortia had similar levels of metabolic activity; when one population had high activity, the associated partner microorganisms were also equally active--consistent with a beneficial symbiosis. However, a close look at the spatial organization of the cells revealed that no particular arrangement of the two types of organisms--whether evenly dispersed or in separate groups--was correlated with a cell's activity.

To determine how these metabolic interactions were taking place even over relatively long distances, postdoctoral scholar and coauthor Chris Kempes, a visitor in computing and mathematical sciences, modeled the predicted relationship between cellular activity and distance between syntrophic partners that are dependent on the molecular diffusion of a substrate. He found that conventional metabolites--molecules previously predicted to be involved in this syntrophic consumption of methane--such as hydrogen--were inconsistent with the spatial activity patterns observed in the data. However, revised models indicated that electrons could likely make the trip from cell to cell across greater distances.

"Chris came up with a generalized model for the methane-oxidizing syntrophy based on direct electron transfer, and these model results were a better match to our empirical data," Orphan says. "This pointed to the possibility that these archaea were directly transferring electrons derived from methane to the outside of the cell, and those electrons were being passed to the bacteria directly."

Guided by this information, Chadwick and McGlynn looked for independent evidence to support the possibility of direct interspecies electron transfer. Cultured bacteria, such as those from the genus Geobacter, are model organisms for the direct electron transfer process. These bacteria use large proteins, called multi-heme cytochromes, on their outer surface that act as conductive "wires" for the transport of electrons.

Using genome analysis--along with transmission electron microscopy and a stain that reacts with these multi-heme cytochromes--the researchers showed that these conductive proteins were also present on the outer surface of the archaea they were studying. And that finding, Orphan says, can explain why the spatial arrangement of the syntrophic partners does not seem to affect their relationship or activity.

"It's really one of the first examples of direct interspecies electron transfer occurring between uncultured microorganisms in the environment. Our hunch is that this is going to be more common than is currently recognized," she says.

Orphan notes that the information they have learned about this relationship will help to expand how researchers think about interspecies microbial interactions in nature. In addition, the microscale stable isotope approach used in the current study can be used to evaluate interspecies electron transport and other forms of microbial symbiosis occurring in the environment.

###

These results were published in a paper titled, "Single cell activity reveals direct electron transfer in methanotrophic consortia." The work was funded by the Department of Energy Division of Biological and Environmental Research and the Gordon and Betty Moore Foundation Marine Microbiology Initiative.

Media Contact

Deborah Williams-Hedges
debwms@caltech.edu
626-395-3227

 @caltech

http://www.caltech.edu 

Deborah Williams-Hedges | EurekAlert!

Further reports about: Electrons activity bacteria bacterial cellular activity isotope microbes microorganisms symbiosis

More articles from Life Sciences:

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

nachricht Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>