Navigation Links
Bacterial plasmids -- the freeloading and the heavy-lifters -- balance the high price of disease

BLOOMINGTON, Ind. -- 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."

Contact: Steve Chaplin
Indiana University

Related biology news :

1. Gene against bacterial attack unravelled
2. Predatory bacterial swarm uses rippling motion to reach prey
3. Nature study demonstrates that bacterial clotting depends on clustering
4. Shifts in soil bacterial populations linked to wetland restoration success
5. Caltech researchers get first 3-D glimpse of bacterial cell-wall architecture
6. Scientists present moving theory behind bacterial decision-making
7. Scientists build roach motel for nasty bugs of the bacterial variety
8. Bacterial biofilms as fossil makers
9. Winter brings flu, summer brings bacterial infections
10. Computation and genomics data drive bacterial research into new golden age
11. New research lights up chronic bacterial infection inside bone
Post Your Comments:
Related Image:
Bacterial plasmids -- the freeloading and the heavy-lifters -- balance the high price of disease
(Date:11/17/2015)... Pressure BioSciences, Inc. (OTCQB: PBIO) ("PBI" and ... of broadly enabling, pressure cycling technology ("PCT")-based sample preparation ... it has received gross proceeds of $745,000 from an ... "Offering"), increasing the total amount raised to date in ... are expected in the near future. ...
(Date:11/12/2015)... 2015  Arxspan has entered into an agreement ... for use of its ArxLab cloud-based suite of ... partnership will support the institute,s efforts to electronically ... information internally and with external collaborators. The ArxLab ... the Institute,s electronic laboratory notebook, compound and assay ...
(Date:11/10/2015)...  In this report, the biomarkers market ... type, application, disease indication, and geography. The ... consumables, services, software. The type segments included ... biomarkers, and validation biomarkers. The applications segments ... drug discovery and development, personalized medicine, disease ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... ... 2015 , ... Copper is an essential micronutrient that all ... copper is also toxic to cells. With a $1.3 million award from the ... a systematic study of copper in the bacteria Pseudomonas aeruginosa (P. aeruginosa), a ...
(Date:11/24/2015)... PUNE, India , November 24, 2015 ... to a new market research report "Oligonucleotide Synthesis Market ... Equipment), Application (PCR, Gene Synthesis, Diagnostic, DNA, RNAi), End-User ... to 2020", published by MarketsandMarkets, the market is expected ... 1,078.1 Million in 2015, at a CAGR of 10.1% ...
(Date:11/24/2015)... --> --> ... by Transparency Market Research, the global non-invasive prenatal testing ... 17.5% during the period between 2014 and 2022. The ... Analysis, Size, Volume, Share, Growth, Trends and Forecast 2014 ... to reach a valuation of US$2.38 bn by 2022. ...
(Date:11/24/2015)... ... November 24, 2015 , ... In harsh industrial processes, the ... in-line sensors can represent a weak spot where leaking process media is a ... sensor housings , which are designed to tolerate extreme process conditions. They combine ...
Breaking Biology Technology: