More than a mile beneath the ocean’s surface, as dark clouds of mineral-rich water billow from seafloor hot springs called hydrothermal vents, unseen armies of viruses and bacteria wage war.
Like pirates boarding a treasure-laden ship, the viruses infect bacterial cells to get the loot: tiny globules of elemental sulfur stored inside the bacterial cells.
Image courtesy of MARUM, University of Bremen and NOAA-Pacific Marine Environmental Laboratory.
Black smoke from the top of a "chimney" in the Lau Basin in the western Pacific Ocean. Water samples collected by an unmanned submarine revealed how viruses hijack deep-sea bacteria at hydrothermal vents.
Instead of absconding with their prize, the viruses force the bacteria to burn the valuable sulfur reserves, then use the unleashed energy to replicate, eventually filling the bacterial cells to the bursting point.
“Our findings suggest that viruses in the dark oceans indirectly access vast energy sources in the form of elemental sulfur,” said University of Michigan marine microbiologist and oceanographer Gregory J. Dick, whose team collected DNA from deep-sea microbes in seawater samples from hydrothermal vent sites in the western Pacific Ocean and the Gulf of California.
The study identifies viruses as key players in the thriving ecosystems – which include exotic 6-foot tube worms, giant clams and mussels, as well as shrimp – huddled around deep-sea hydrothermal vents.
In addition, they hint that the viruses act as agents of evolution in chemosynthetic systems by swapping genes with the bacteria, Dick said. “We suggest that the viruses serve as a reservoir of genetic diversity that helps shape bacterial evolution,” he said.
A paper summarizing the findings is scheduled for online publication May 1 in Science. The first author is Karthik Anantharaman, a doctoral student in Dick’s lab at the Department of Earth and Environmental Sciences.
Similar microbial interactions have been observed in shallow ocean waters between photosynthetic bacteria and the viruses that prey on them. But this is the first time such a relationship has been seen in a chemosynthetic system, one in which the microbes rely solely on inorganic compounds, rather than sunshine, as their energy source.
Dick and his colleagues collected water samples during trips to the Eastern Lau Spreading Center in the Western Pacific and the Guaymas Basin in the Gulf of California. An unmanned submarine from the Woods Hole Oceanographic Institution captured the samples, at a depth of more than 6,000 feet, near “black smokers” spewing mineral-rich seawater at temperatures surpassing 500 degrees Fahrenheit.
Back in the laboratory, the researchers reconstructed near-complete viral and bacterial genomes from the DNA snippets retrieved at six hydrothermal vent plumes. In addition to the common sulfur-consuming bacterium SUP05, they found genes from five previously unknown viruses.
The genetic data suggest that the viruses prey on SUP05. That’s not too surprising, since viruses are the most abundant biological entities in the oceans and are a pervasive cause of mortality among marine microorganisms.
The real surprise is that the viral DNA contains genes closely related to SUP05 genes used to extract energy from sulfur compounds.
When combined with results from previous studies, this finding suggests that the viruses force SUP05 bacteria to use viral SUP05-like genes to help process stored globules of elemental sulfur. The SUP05-like viral genes are called auxiliary metabolic genes.
“We hypothesize that the viruses enhance bacterial consumption of this elemental sulfur, to the benefit of the viruses,” said co-author Melissa Duhaime, an assistant research scientist in the U-M Department of Ecology and Evolutionary Biology. The revved-up metabolic reactions may release energy that the viruses then use to replicate and spread.
“We suspect that these viruses are essentially hijacking bacterial cells and getting them to consume elemental sulfur so the viruses can propagate themselves,” Anantharaman said.
But how did SUP05-like genes end up in these viruses? The researchers can’t say for sure, but presumably the viruses snatched genes from SUP05 during some ancient microbial interaction.
“There seems to have been an exchange of genes, which implicates the viruses as an agent of evolution. That’s interesting from an evolutionary biology standpoint,” Dick said.
The new microbial findings will help researchers understand how marine biogeochemical cycles, including the sulfur cycle, will respond to global environmental changes such as the ongoing expansion of dead zones. SUP05 bacteria, which may generate the greenhouse gas nitrous oxide, will likely expand their range as oxygen-starved zones continue to grow in the oceans.
In addition to Anantharaman, Dick and Duhaime, authors of the Science paper are John A. Breir of the Woods Hole Oceanographic Institution, Kathleen Wendt of the University of Minnesota and Brandy M. Toner of the University of Minnesota.
The project was funded in part by the Gordon and Betty Moore Foundation through grants GBMF2609 and GBMF2764; the National Science Foundation through grants OCE-1038006, OCE-1038055, OCE-1037991 and OCE-1029242; and the U-M Rackham Graduate School Faculty Research Fellowship Program.
“Viruses play a cardinal role in biogeochemical processes in the ocean’s shallow and mid-to-deeper waters,” said David Garrison, program director in the National Science Foundation’s Division of Ocean Sciences, which funded the research. “This study suggests that viruses may have a similar importance in deep-sea thermal vent environments.”
Jim Erickson | newswise
Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation
Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)
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...
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...
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...
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...
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...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences