Featured Research

from universities, journals, and other organizations

Interspecies electron transfer: Anaerobic bacteria found to cooperate

Date:
December 4, 2010
Source:
University of Massachusetts at Amherst
Summary:
Microbiologists report that they have discovered a new cooperative behavior in anaerobic bacteria, known as interspecies electron transfer, that could have important implications for the global carbon cycle and bioenergy.

Cells in aggregate.
Credit: Image courtesy of University of Massachusetts at Amherst

University of Massachusetts Amherst microbiologists Derek Lovley, Zarath Summers and colleagues report in the Dec. 2 issue of Science that they have discovered a new cooperative behavior in anaerobic bacteria, known as interspecies electron transfer, that could have important implications for the global carbon cycle and bioenergy.

The scientists found that microorganisms of different species, in this case two Geobacter species, can form direct electrical connections and pass an electric current from one microbe to the other. By cooperating in this way the two microbes can consume food that neither of them could use on their own.

The cell aggregates or "great balls of evolution" that Summers evolved in the laboratory look very much like those found in nature which are involved in degrading organic matter into the greenhouse gases, carbon dioxide and methane. Conversion of wastes to methane by microbial aggregates is an increasingly popular method for producing natural gas as an renewable energy source.

Others can be found consuming methane from vents at the bottom of the ocean. In both cases, investigators have been puzzled for years about how these aggregates function, because a 40-year-old interspecies hydrogen transfer paradigm did not seem to fit observations. Now, the mystery appears to be solved.

As Lovley, the principal investestigator, explains, "We placed the microbes under conditions in which they had to work together in order to survive and grow using the alcohol we gave them as an energy source. They're the ultimate drinking buddies, collaborating to consume ethanol." With support from the Genomic Science Program of the U.S. Department of Energy, his lab has been exploiting the ability of microorganisms to adapt to novel conditions and developing microbes for practical applications.

It's been known since the 1960s that microorganisms can indirectly exchange electrons by the process known as interspecies hydrogen transfer. In it, one microbe produces hydrogen that another microbe then consumes. It was experiments carried out by doctoral candidate Summers to explore this phenomenon further that led to discovery of the new direct transfer process.

To begin, Summers put two species of Geobacter together under conditions expected to favor hydrogen-sharing interactions. At first, the cells did cooperate to consume the alcohol by sharing hydrogen. Over time, they also started clumping together and transforming the culture from one of dispersed microscopic cells, invisible to the naked eye, to a collection of complex multi-cellular structures, millimeters in diameter.

Resisting her lab mates' urgings to shake the cultures and break up the unexpected cell clumps, Summers continued to allow the spheres to grow. Now they were exhibiting a deep red color due to the presence of iron-containing proteins known as cytochromes. When observed with an electron microscope, they had clearly developed an intricate structure with a series of channels, presumably to help nutrients enter. They had also established completely new electric connections that permitted them to directly share electrons.

"The direct electron transfer is much more efficient and they consume alcohol much faster this way," Summers points out. Sequencing the DNA in the big red balls revealed the secret to this electrical connection: a mutation in one of the Geobacter species had caused it to make much more of a cytochrome known as OmcS. Previous studies in Lovely's lab had shown that OmcS lines up along Geobacter's electrically conductive filaments known as microbial nanowires.

"This turn of events suggested that the cytochrome was key to the electrical connection between the cells" says Summers. This was confirmed in subsequent experiments with genetically manipulated microbes. When the researchers deleted genes for the cytochrome or the nanowires, the microbes did not form the red balls and never effectively used their alcohol fuel. Lovley, Summers and colleagues had thus pinpointed the source of the microbes' new behavior.

Further experiments showed that if the mutation was introduced before putting the two Geobacters together, they rapidly formed the balls and consumed alcohol. Deleting a gene that would be necessary for the cells to exchange hydrogen also hastened ball formation, demonstrating that interspecies hydrogen transfer was not an important factor. "This is a clear case of life evolving to function more effectively in a new environment" says Lovley.

"We're guessing that many types of natural aggregates rely on interspecies electron transfer" said Lovley. "We already have some good preliminary evidence for this with some more complex natural systems. With DNA sequencing we can determine how the microbes evolve when challenged to do better. We can learn a lot about the basic mechanisms of the process of interest," he adds.


Story Source:

The above story is based on materials provided by University of Massachusetts at Amherst. Note: Materials may be edited for content and length.


Journal Reference:

  1. Z. M. Summers, H. E. Fogarty, C. Leang, A. E. Franks, N. S. Malvankar, D. R. Lovley. Direct Exchange of Electrons Within Aggregates of an Evolved Syntrophic Coculture of Anaerobic Bacteria. Science, 2010; 330 (6009): 1413 DOI: 10.1126/science.1196526

Cite This Page:

University of Massachusetts at Amherst. "Interspecies electron transfer: Anaerobic bacteria found to cooperate." ScienceDaily. ScienceDaily, 4 December 2010. <www.sciencedaily.com/releases/2010/12/101202141914.htm>.
University of Massachusetts at Amherst. (2010, December 4). Interspecies electron transfer: Anaerobic bacteria found to cooperate. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2010/12/101202141914.htm
University of Massachusetts at Amherst. "Interspecies electron transfer: Anaerobic bacteria found to cooperate." ScienceDaily. www.sciencedaily.com/releases/2010/12/101202141914.htm (accessed September 20, 2014).

Share This



More Earth & Climate News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Wildfires in CA Burn Forest Asunder

Raw: Wildfires in CA Burn Forest Asunder

AP (Sep. 18, 2014) An out-of-control Northern California wildfire has nearly 2,800 people from their homes as it continues to grow, authorities said Thursday. Authorities said a man has been arrested on suspicion of arson for starting the fire on Saturday. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins