New pathways in bacterial intercellular competition uncovered

Apr 08, 2013
From left are Christopher Hayes, Sanna Koskiniemi, and James Lamoureux in the Hayes laboratory at UCSB. Credit: George Foulsham

(Phys.org) —There's an epic battle taking place that's not on the national radar: intercellular competition. While it's not an Olympic event, new research from UC Santa Barbara demonstrates that this microscopic rivalry can be just as fierce as humans going for the gold.

Christopher Hayes, UCSB associate professor of molecular, cellular and , along with postdoctoral fellow Sanna Koskiniemi, graduate student James Lamoureux, and others, examined the role certain proteins, called rearrangement hotspots (Rhs), play in intercellular in bacteria. The findings appear today in the Proceedings of the National Academy of Sciences.

Rhs proteins and related YD-peptide repeat proteins are present in a wide range of and other organisms, including human beings, where they help establish communications between neurons in the brain when the visual system is developing. Hayes and his team found that Rhs proteins enable Dickeya dadantii 3937, a phytopathogenic bacterium causing soft rot diseases on many crops, to compete with members of its own kind through touch-dependent killing.

While Rhs have been recognized for more 30 years, their function has been enigmatic. This new research sheds light on the mystery. Rhs proteins possess a central repeat region, characteristically the YD-repeat proteins also found in humans, as well as variable C-terminal sequences, which have toxin activity. C-terminal regions are highly variable between even in the same species, indicating that a wide variety of weapons are deployed.

"Bacteria almost always have a different Rhs toxins," explained Hayes. "No one really knows why, but perhaps the toxins are rapidly evolving, driven by intercellular competition. In essence, these cells are fighting it out with each other. It's like an arms race to see who has the best toxins."

Cellular competition is analogous to that between humans and reflects a scarcity of resources. Like people, bacteria need a place to live and food to eat. "We think these systems are important for bacterial cells to establish a home and defend it against competitors," said Hayes. "In fact, bacteria have many systems for competition. And as we uncover more mechanisms for intercellular competition, we realize this is a fundamental aspect of bacterial biology."

These findings demonstrate that Rhs systems in diverse bacterial species are toxin delivery machines. "We have been able to show that gram-negative (Dickeya dadantii) as well as gram-positive (Bacillus subtilis) bacteria use Rhs proteins to inhibit the growth of neighboring bacteria in a manner that requires cell-to-cell contact," said Koskiniemi, the paper's lead author.

The toxic part of Rhs at the tip (the C-terminal region) is delivered into target cells after cell-to-cell contact. Some toxic tips destroy DNA and others destroy transfer RNA, which is essential for synthesis. These toxin activities help the bacteria expressing them to outcompete other members of the same species not carrying an antidote.

This work may help scientists design Rhs-based bacterial probiotics that kill specific pathogens but leave most normal flora unharmed. The research was supported by grants from the National Science Foundation and National Institutes of Health and by fellowships from the Carl Tryggers and Wenner-Gren Foundations.

Explore further: Researchers successfully clone adult human stem cells

Related Stories

Researchers suggests that bacteria communicate by touch

Mar 01, 2012

What if bacteria could talk to each other? What if they had a sense of touch? A new study by researchers at UC Santa Barbara suggests both, and theorizes that such cells may, in fact, need to communicate in ...

Revealing the weapons by which bacteria fight each other

Apr 04, 2013

A new study which was performed jointly at Umea University and the University of Washington in Seattle, USA, discovered that bacteria can degrade the cell membrane of bacterial competitors with enzymes that do not harm their ...

Recommended for you

Researchers successfully clone adult human stem cells

Apr 18, 2014

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Researchers develop new model of cellular movement

Apr 18, 2014

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

For resetting circadian rhythms, neural cooperation is key

Apr 17, 2014

Fruit flies are pretty predictable when it comes to scheduling their days, with peaks of activity at dawn and dusk and rest times in between. Now, researchers reporting in the Cell Press journal Cell Reports on April 17th h ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

PPihkala
not rated yet Apr 09, 2013
If these are rapidly evolving bacterial toxins, then using these will not give very long lasting effect. Like what was discovered when penisillin was used. Many current strains are resistant to it.
BetAmakeR
not rated yet Apr 10, 2013
at least for short term preventive measure

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...