Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bacterial Plasmids -- the Freeloading and the Heavy-Lifters -- Balance the High Price of Disease

06.02.2012
Studying self-replicating genetic units, called plasmids, found in one of the world's widest-ranging pathogenic soil bacteria -- the crown-gall-disease-causing microorganism Agrobacterium tumefaciens -- Indiana University biologists are showing how freeloading, mutant derivatives of these plasmids benefit while the virulent, disease-causing plasmids do the heavy-lifting of initiating infection in plant hosts.

The research confirms that the ability of bacteria to cause disease comes at a significant cost that is only counterbalanced by the benefits they experience from infected host organisms.

A. tumefaciens is widely studied for its remarkable biology not only because it causes disease in over 140 genera of broadleaf plants, including fruit trees, grapes, roses and walnut trees, but also because it is considered one of the most important tools for plant biotechnology: It is the only organism known to routinely engage in inter-kingdom lateral gene transfer. A. tumefaciens infects host plants by transferring a portion of its own DNA into plant cells, and this integrated bacterial DNA is expressed in the plant cells, leading diseased plants to develop tumors and produce resources that benefit the pathogen.

"We've identified two types of costs the plant pathogen A. tumefaciens pays for traits conferred by genes carried on plasmids," said lead author Thomas G. Platt, a postdoctoral researcher in the IU Bloomington College of Arts and Sciences' Department of Biology. "There is a relatively low cost of maintaining the tumor-inducing virulence plasmid, but there is also a dramatically large cost of expressing the genes that are required to infect plants."

Plants with crown gall disease can also benefit a second type of plasmid that can be found in A. tumefaciens: Nonpathogenic plasmids that lack the genes required to infect plants, yet are still able to benefit from the breakdown of nutrient resources released by infected plant tissue.

"These nonvirulent strains are able to freeload on public goods produced by host plants infected by their disease-causing relatives, while themselves avoiding the burdens associated with A. tumefaciens' virulence plasmid," Platt explained. "And our results suggest that at least one source of the selective pressure favoring the spread of these avirulent mutants stems from those high costs associated with the expression of the genes underlying pathogenesis."

Scientists are especially interested in freeloading or cheating strains of bacteria as a possible means of constraining infection caused by more aggressive, pathogenic strains. Creating something of a balancing act, mutant cheater strains may counter or constrain virulence as they maintain higher fitness by not having to invest in the cellular machinery virulent bacteria employ to infect hosts.

"The population dynamics and maintenance of bacterial plasmids depend on the costs they impose and benefits they confer on the cells that host them, and those costs and benefits are environmentally context dependent," Platt said. "The outcome of competition between two agrobacteria strains such as the ones we have been studying varies with the environmental conditions in which they are competing, and this genotype-by-genotype-by-environment interaction suggests that the virulence plasmid may be subject to selective pressures that vary over space and time."

Platt and IU biology professors James D. Bever and Clay Fuqua recently published the measured fitness costs imposed by plasmids to host cells, under certain environmental conditions, in the research article "A cooperative virulence plasmid imposes a high fitness cost under conditions that induce pathogenesis," that appeared in Proceedings of the Royal Society B. That work will be expanded upon in research accepted for publication in an upcoming edition of the journal Evolution, where the team further examines how cooperation benefits depend on resource availability and the importance of ecological dynamics, including resource consumption and population growth, on the evolution of cooperative traits.

To speak with Platt or for more information, please contact Steve Chaplin, IU Communications, at 812-856-1896 or stjchap@iu.edu. Tweeting Indiana University science: @IndianaScience

Steve Chaplin | Newswise Science News
Further information:
http://www.iu.edu

More articles from Life Sciences:

nachricht Water world
20.11.2017 | Washington University in St. Louis

nachricht Carefully crafted light pulses control neuron activity
20.11.2017 | University of Illinois at Urbana-Champaign

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>