Disease-causing bacteria compete with human hosts for key micronutrient, study shows

New research from a University of Florida microbiologist shows that disease-causing bacteria compete with their human hosts for a key micronutrient.

Although queuine (pronounced KYOO-in) has been identified as essential to human health – a 2018 study by Bruce Ames referred to it as a "longevity vitamin" – much is still unknown about the compound that humans must obtain from their natural gut bacteria, or secondarily, through dietary sources.

"Usually, bacteria make queuine from scratch," said Valérie de Crécy-Lagard, a professor in the UF/IFAS department of microbiology and cell science whose just-published paper detailing the discovery appears in the journal PNAS. "What we found is that some bacteria that live in the human environment are not making it from scratch; instead, they're competing for the same micronutrients as the human host."

All multi-celled organisms rely on single-celled ones, bacteria, to synthesize queuine. The human gut naturally has these queuine manufacturers, or they enter the body through the plant and animal sources we consume. Humans are able to recover the queuine we need through what are known as salvage enzymes, de Crécy-Lagard said.

The study was done in collaboration with scientists from the University of Illinois, Pasteur Institute, Massachusetts Institute of Technology and Albert Einstein College of Medicine. It utilized computer-driven data mining to investigate queuine metabolism in two pathogenic, or disease-causing, bacteria: Chlamydia trachomatis, commonly known as the sexually transmitted disease chlamydia, and Clostridioides difficile, sometimes shortened to C. diff, that causes diarrhea and other intestinal issues and involves abnormal gut bacteria levels.

We don't really know yet how queuine is important in these pathogens, but it must be important because the queuine salvage enzymes are there, too. Scientists didn't previously think that bacteria would compete with a human host for this micronutrient."

Valérie de Crécy-Lagard, professor, department of microbiology and cell science, UF/IFAS

The presence of queuine salvage enzymes in these bacteria, which makes this competition possible, were a brand-new discovery, de Crécy-Lagard added.

"The bacteria is essentially behaving like humans by not making its own queuine, instead stealing it through an enzymatic process that had not previously been described," she said. "Next, I want to look at all of the bacteria of the microbiota and looking at all of the exchanges that occur. We want to try and model the interaction between bacteria in the gut and the host."

At this time, queuine is both difficult and expensive to synthesize in a lab. It is not available in any sort of commercial supplements, but according to de Crécy-Lagard, its importance is becoming clearer as more research is done on the micronutrient.

"We are now at a stage where we're asking new questions that don't have answers yet," she said. "But it's putting queuine on the radar."