Washington State University researcher Arden Baylink holds a petri dish containing salmonella bacteria. Credit: Ted S. Warren, Washington State University College of Veterinary Medicine
Key points:
- Researchers discovered that some bacteria are attracted to the liquid part of blood, or serum, which contains nutrients the bacteria can use as food.
- Salmonella seemed particularly drawn to was serine, an amino acid found in human blood that is also a common ingredient in protein drinks.
- The team says this line of research could drastically improve the lives and health of people with IBD, who are at high risk for bloodstream infections.
In a newly discovered phenomenon researchers have dubbed “bacterial vampirism,” some of the world's deadliest bacteria seem to seek out and feed on human blood.
A team of Washington State University researchers found that bacteria are attracted to the liquid part of blood, which contains nutrients the bacteria can use as food. One of the chemicals the bacteria seemed particularly drawn to was serine, an amino acid found in human blood that is also a common ingredient in protein drinks. The finding provides new insights into how bloodstream infections occur and could potentially be treated.
Using a high-powered microscope system designed by WSU professor Arden Baylink, called the Chemosensory Injection Rig Assay, the researchers simulated intestinal bleeding by injecting microscopic amounts of human serum and watching as the bacteria navigated toward the source. The response was rapid—less than a minute for the disease-causing bacteria to find the serum.
According to the study results published in eLife, at least three types of bacteria—Salmonella enterica, Escherichia coli and Citrobacter koseri—were attracted to human serum. These bacteria are a leading cause of death for people who have inflammatory bowel diseases (IBD), about 1% of the population. These patients often have intestinal bleeding that can be entry points for the bacteria into the bloodstream.
“Bacteria infecting the bloodstream can be lethal,” said Baylink, corresponding author for the research. “We learned some of the bacteria that most commonly cause bloodstream infections actually sense a chemical in human blood and swim toward it.”
Looking specifically at Salmonella, the team found that the bacteria have a special protein receptor called Tsr, which enables it to sense and swim toward serum. Using protein crystallography, they were able to view the atoms of the protein interacting with serine. The scientists believe serine is one of the chemicals from blood that the bacteria sense and consume.
“By learning how these bacteria are able to detect sources of blood, in the future we could develop new drugs that block this ability. These medicines could improve the lives and health of people with IBD who are at high risk for bloodstream infections,” said lead author of the study, WSU Ph.D. student Siena Glenn.