Cellular changes may account for rapid infection by Salmonella in humans

Salmonella is a type of bacteria that causes food poisoning which, on occasion, can spread to a person’s entire body and cause life-threatening illness. The bacteria are also linked to chronic inflammatory conditions such as arthritis.  

Researchers at The Hospital for Sick Children (SickKids) have identified cellular changes that reveal how Salmonella can infect a cell, a finding which may help scientists develop future treatments and improve patient outcomes. 

Led by Dr. John Brumell, Senior Scientist and Program Head of the Cell Biology program, research published in Nature Communications discovered that extra cell membrane is recruited by Salmonella to help the bacteria gain access into a cell.  

“These reservoirs of cell membrane may have other important biological functions under healthy conditions,” Brumell says. “We may have opened up a whole new area of cell biology.”

Cellular structures help Salmonella bacteria infect faster

When Salmonella invades a human cell, the bacteria are engulfed by the cell’s membrane in a large structure called a ruffle – like tree branches extending outward from the cell to surround the bacteria. Since these ruffles require a significant rearrangement of the cell’s membrane, the research team wanted to know how the structures were formed.

Using specialized instruments at the SickKids Imaging Facility and the SickKids Nanoscale Biomedical Imaging Facility, the researchers were able to visualize the process of a cellular ruffle forming. They observed that RAB10, a human protein involved in a wide range of cellular processes, exists within cells in tube-like structures, which the research team identified as a part of a cell’s membrane. Due to their shape, the team believes that these tubular structures act like highways that allow the cell’s surface to make contact with multiple organelles within the cell. 

Within 10 minutes of Salmonella infection, the bacteria break down the tubular structures that hold extra cell membrane and transform it into large cellular ruffles. These ruffles change the shape of a cell’s membrane in favour of the bacteria, allowing the bacteria to enter the cell more easily – something researchers are interested in stopping. 

“We found that Salmonella has a very robust ability to redirect membrane reservoirs and to use them to invade into a host cell,” says Brumell, who is also the Co-Director of SickKids’ Inflammatory Bowel Disease Centre. “But these structures may have implications beyond Salmonella, and we’re excited to explore what opportunities this may present.” 

The team’s future research will explore if other bacteria have a similar ability to use these cell membrane reservoirs during infection. 

This research was supported by the Canadian Institutes of Health Research (CIHR), the Natural Sciences and Engineering Research Council of Canada, the Leona M. and Harry B. Helmsley Charitable Trust (A.M.M.) and the National Institutes of Health Research.