In a recent study published in the Proceedings of the National Academy of Sciences, scientists used a powerful microscope to observe small molecular machines that bacteria use to infect host cells. This new finding is vital for the development of anti-bacterial drugs to fight infectious diseases.
In the study titled “Visualization of the type III secretion sorting platform of Shigella flexneri,” funded by the National Institute of Allergy and Infectious Diseases, the team from the University of Texas Health Science Center at Houston (UTHealth), Dalhousie University in Halifax, Nova Scotia, and the University of Kansas, Lawrence, used a secretion machine called injectisome.
The injectisome is like a hypodermic needle that punctures the organism’s outer layer to insert a specific disease agent. The team investigated the “secretion machine” linked with Shigella flexneri, salmonella, and other pathogens. According to Dr. William Margolin, study co-author, this new finding can improve our understating of the structure of the “machine” and be used to identify new drugs.
“We combined cutting-edge imaging and genetic techniques to visualize the frozen-hydrated diarrheal pathogen Shigella flexneri and reveal the intact type III secretion machine and its interaction with a host cell for the first time,” Dr. Jun Liu, study’s senior author and a professor of pathology and laboratory medicine, said in a news release. The team used an electron microscope to look at a cryogenic hydrated specimen, which was then loaded in the scope, with images collected using a new-generation direct electron detector.
“This study uses novel approaches to characterize the intact type III secretion machinery showing how virulent shigella strains interact with host tissues,” added Dr. Herbert DuPont, director of the Center for Infectious Diseases at UTHealth School of Public Health, who is also a holder of the Mary W. Kelsey Chair in the Medical Sciences at UTHealth Medical School.
Salmonella is estimated to affect nearly 1.2 million people in the US alone, causing 19,000 hospitalizations and 380 deaths each year, according to the Centers for Disease Control and Prevention. The bacterium causes fever, diarrhea, and abdominal cramps about 12 to 72 hours following infection. Additionally, Shigella is estimated to infect 80 to 165 million people every year, resulting in approximately 600,000 deaths.
According to the news release, the authors stated the magnitude of this study can be compared to Google Earth. “It was like Google Earth in that you are able to zoom in on tiny molecular machines. But unlike Google Earth in which many of the streets and boulevards are already known, we were charting new areas and making new maps. You could call it cartography,” said Dr. Morado, a UTHealth research assistant.