How does the bacterium Shigella detect that it's in a human host? Shigella is the cause of a deadly diarrheal disease. According to a study published May 21 in the journal PLOS ONE, 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. The scientists have been seeking more information about the genetic pathways 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 molecular and cellular biology, 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 messenger RNA was inhibited. The scientists suggest that the structure of the RNA thermometer was blocking genetic expression by preventing protein synthesis.
"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.