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 firstname.lastname@example.org. Tweeting Indiana University science: @IndianaScience
Steve Chaplin | Newswise Science News
Transport of molecular motors into cilia
28.03.2017 | Aarhus University
Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences