Bacterium uses natural 'thermometer' to trigger diarrheal disease, scientists find

May 21, 2013

How does the bacterium Shigella—the cause of a deadly diarrheal disease—detect that it's in a human host? Ohio University scientists have found that a biological "RNA thermometer" monitors whether the environment is right for the bacterium to produce the factors it needs to survive within the body, according to a study published May 21 in the journal PLOS ONE.

The scientists have been seeking more information about the of Shigella in the hope of finding new treatment options for the disease it causes. Shigellosis kills more than a million people worldwide each year and is becoming more resistant to antibiotics, said Erin Murphy, an assistant professor in Ohio University's Heritage College of Osteopathic Medicine.

The recent study led by Murphy and Andrew Kouse, a doctoral student in , found that when Shigella was in a 37 degree Celsius environment (or at "body temperature"), it efficiently produced the ShuA protein from the corresponding messenger RNA molecule. The bacterium needs the ShuA protein to obtain iron from heme, the most abundant source of this essential nutrient within the human body. Without iron, the invading Shigella would not survive, Murphy explained.

At room temperature, 25 degrees Celsius, production of the ShuA protein from the corresponding was inhibited. The scientists suggest that the structure of the RNA thermometer was blocking genetic expression by preventing .

"This may be an , as it would be wasteful for the bacterium to make this protein before it was in the host," Murphy said.

But once at body temperature, part of the structure of the thermometer "melts away," she said, triggering the bacterium to synthesize the ShuA protein.

The new study marks the first time that researchers have observed a "RNA thermometer" in the Shigella bacterium.

This particular thermometer belongs to a subclass called "FourU RNA thermometers" that was first characterized by study co-author Franz Narberhaus of the Ruhr University Bochum, Germany. These thermometers have been identified in only two other bacteria, Salmonella and Yersinia, both of which can cause serious human illnesses.

"I find it fascinating that an entirely new class of genes has been found to be controlled by an RNA thermometer," Narberhaus said.

Now that the scientists have identified the RNA thermometer in the ShuA gene, they'll look for this structure in the other genes that regulate Shigella's ability to survive in the human host and cause disease.

"The findings could have practical implications for drug design," Murphy said.

Explore further: It slices, it dices, it silences: ADAR1 as gene-silencing modular RNA multitool

More information: dx.plos.org/10.1371/journal.pone.0063781

Related Stories

Human cells build protein cages to trap invading Shigella

Dec 04, 2011

In research on the never-ending war between pathogen and host, scientists at the Pasteur Institute in Paris have discovered a novel defensive weapon, a cytoskeletal protein called septin, that humans cells deploy to cage ...

Recommended for you

Ocean microbes display remarkable genetic diversity

11 hours ago

The smallest, most abundant marine microbe, Prochlorococcus, is a photosynthetic bacteria species essential to the marine ecosystem. An estimated billion billion billion of the single-cell creatures live i ...

Cell resiliency surprises scientists

13 hours ago

New research shows that cells are more resilient in taking care of their DNA than scientists originally thought. Even when missing critical components, cells can adapt and make copies of their DNA in an alternative ...

Cell division speed influences gene architecture

Apr 23, 2014

Speed-reading is a technique used to read quickly. It involves visual searching for clues to meaning and skipping non-essential words and/ or sentences. Similarly to humans, biological systems are sometimes ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

PPihkala
1 / 5 (1) May 21, 2013
Now make something similar to this RNA thermometer that is stable at human temperatures and use that as a drug to keep shigella in check in infected people.

More news stories

Genetic code of the deadly tsetse fly unraveled

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals.

Ocean microbes display remarkable genetic diversity

The smallest, most abundant marine microbe, Prochlorococcus, is a photosynthetic bacteria species essential to the marine ecosystem. An estimated billion billion billion of the single-cell creatures live i ...

Cell resiliency surprises scientists

New research shows that cells are more resilient in taking care of their DNA than scientists originally thought. Even when missing critical components, cells can adapt and make copies of their DNA in an alternative ...