Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Aphids Saved From Gruesome Death by Virus-Infected Bacteria

21.08.2009
The term "beneficial virus" sounds like an oxymoron.

But for pea aphids under attack by parasitic wasps, carrying infected bacteria is the difference between life and a slow death, according to new research from The University of Arizona in Tucson.

The wasps lay eggs inside the aphids, and the wasp larvae eat the living aphids from the inside out.

"A parasitoid death would be a very gruesome death," said first author Kerry M. Oliver. "It's like the movie 'Alien' where this thing grows inside of you and then ruptures out of you and kills you."

In laboratory experiments, about eighty percent of aphids carrying uninfected Hamiltonella defensa bacteria died as a result of wasp attacks.

However, most of the aphids whose H. defensa bacteria had a particular virus did survive wasp attacks.

The research is the first demonstration that a virus that infects bacteria can help rather than harm the bacteria's animal host, said Oliver, who

earned his doctorate at the UA.

The researchers also tested strains of aphids whose bacteria had once been
infected but were no longer.
"In every instance where the virus was lost, protection was lost almost completely," said Oliver, now an assistant professor at the University of Georgia in Athens.

The virus, known as APSE, carries genes that code for toxins the researchers think are involved in the anti-wasp defense.

By contrast, being infected by viruses toting toxin codes often makes disease-causing bacteria such as E. coli more, not less, harmful to their human hosts.

Biologists call the part of the APSE viral DNA that codes for toxins a "mobile genetic element." The virus can and does move that mobile genetic element between individual bacteria and between different species of bacteria, Moran said.

The mobile genetic element can become incorporated into the recipient's DNA, giving the recipient the ability to make the toxin.

Species-to-species transmission of DNA via mobile genetic element is quite different from the well-known means by which parents pass on their genetic material to their offspring. In animals, pieces of DNA typically cannot jump from one adult organism's genetic material to another adult organism's genetic material.

"The coolest thing to me is that you can have selection and adaptation for
(wasp) resistance that occurs in one species and then, whoosh, it could suddenly appear in another species," said Moran, a UA Regents' Professor of ecology and evolutionary biology.

Pea aphids can be agricultural pests and Aphidius ervi, the wasp the researchers tested, is used to control aphid populations.

The team's research may also reveal why biological control of aphids with wasps works sometimes but not others, she said.

"Our work suggests it depends which virus the bacteria have."

Oliver and his UA colleagues Patrick H. Degnan, Martha S. Hunter and Nancy A. Moran, will publish their paper, "Bacteriophages Encode Factors Required for Protection in a Symbiotic Mutualism," in the August 21 issue of the journal Science.

Moran, a UA Regents' Professor of ecology and evolutionary biology, has been investigating the role internal symbiotic bacteria play in the lives of the pea aphid Acyrthosiphon pisum for more than 15 years.

Aphids and other insects that feed on sap often house several species of such bacteria. Some, known as primary symbionts, provide aphids with essential nutrients that are not available in the nutrient-poor plant sap.

Aphids cannot survive without their primary symbionts, and those symbionts cannot survive outside of aphids.

The aphid-primary symbiont relationship is so close that the bacteria live inside specialized cells within the aphid.

In addition, aphids often carry other bacteria known as secondary symbionts.
Those are symbionts that are needed for survival and reproduction only under certain conditions, such as the presence of particular enemies.

Oliver, working with Hunter and Moran, discovered that aphids carrying the secondary symbiont Hamiltonella defensa were wasp-resistant, but aphids without H. defensa were susceptible.

But when aphids were kept in the laboratory for generations without being exposed to the wasps, some strains lost their ability to resist wasp attacks, the researchers found.

It turned out that the susceptible aphids still carried the H. defensa bacteria, but the bacteria had lost the APSE virus.

To rule out genetic differences between aphids or bacteria as the source of wasp susceptibility, the researchers needed to do another experiment.

The team compared aphids that had H. defensa with APSE virus to the same strain of aphids carrying the same strain of H. defensa but without the virus.

When exposed to the wasps, about 90 percent of aphids with infected bacteria survived wasp attacks. Aphids without infected bacteria were pretty much doomed.

"It really shows how complicated life is," Oliver said. "It's really a microbial world."

The National Science Foundation, the U.S. Department of Agriculture and the National Institutes of Health funded the research.

Researcher contact information:
Nancy Moran, 520-621-3581, nmoran@email.arizona.edu
Kerry Oliver, 706-542-2311, kmoliver@uga.edu
Related Web sites:
Kerry Oliver
http://www.ent.uga.edu/personnel/faculty/oliver.htm
Nancy Moran's Laboratory
http://eebweb.arizona.edu/faculty/moran/
Martha S. Hunter
http://ag.arizona.edu/ento/faculty/hunter.htm
UA Center for Insect Science
http://cis.arl.arizona.edu/

Mari N. Jensen | University of Arizona
Further information:
http://www.arizona.edu

More articles from Life Sciences:

nachricht Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY

nachricht NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>