Some of the world’s deadliest bacteria seek out and feed on human blood, a newly discovered phenomenon that researchers are calling “bacterial vampirism.”
A team led by researchers at Washington State University has found that bacteria are attracted to the liquid part of blood, or serum, which contains nutrients that bacteria can use as food. One of the chemicals that seemed to particularly attract bacteria was serine, an amino acid found in human blood that is also commonly found in protein drinks.
The research results, published in the journal eLife, provide new insights into how bloodstream infections arise and how they could be treated. “Bacteria that infects the bloodstream can be fatal,” says Arden Baylink, a professor at the WSU College of Veterinary Medicine and an author of the study. “We found that some of the bacteria that most commonly cause bloodstream infections actually recognize a chemical in human blood and swim toward it.”
Baylink and the study’s lead author, WSU graduate student Siena Glenn, found that at least three types of bacteria, Salmonella enterica, Escherichia coli and Citrobacter koseri, are attracted to human serum. These bacteria are a leading cause of death for people suffering from inflammatory bowel disease (IBD), about 1% of the population. These patients often experience intestinal bleeding, which can serve as an entry point for bacteria into the bloodstream.
Using a high-performance microscopy system developed by Baylink called the Chemosensory Injection Rig Assay, the researchers simulated intestinal bleeding by injecting microscopic amounts of human serum and observing how the bacteria navigated to the source. The reaction is quick: it takes less than a minute for the pathogenic bacteria to find the serum.
As part of the study, researchers discovered that Salmonella has a special protein receptor called Tsr, which allows the bacteria to recognize and swim on serum. Using a technique called protein crystallography, they were able to see the atoms in the protein that interact with serine. Scientists believe serine is one of the blood chemicals that bacteria recognize and consume.
“By learning how these bacteria can recognize blood sources, we could develop new drugs in the future that block this ability.” “These drugs could improve the lives and health of people with IBD who are at high risk of bloodstream infections.” says Glenn.
REFERENCE
Bacterial vampirism mediated by taxis to the serum
Photo: Arden Baylink, a researcher at Washington State University, holds a petri dish containing salmonella bacteria. Baylink and graduate student Siena Glenn have published research showing that some of the world’s deadliest bacteria seek out and eat whey, the liquid part of human blood that contains nutrients that bacteria can use as food. Photo credit: Ted S. Warren, Washington State University College of Veterinary Medicine.