Bacterial response to an unusual sugar molecule found in green leafy vegetables could determine their ability to protect and promote gut health, revealed a new study.
The finding suggests that leafy greens are essential for feeding good gut bacteria, limiting the ability of bad bacteria to colonize the gut by shutting them out of the prime 'real estate'.
Researchers from Melbourne and the UK identified a previously unknown enzyme used by bacteria, fungi and other organisms to feed on the unusual but abundant sugar sulfoquinovose - SQ for short - found in green vegetables.
Dr Goddard-Borger said the discovery could be exploited to cultivate the growth of 'good' gut bacteria. "Every time we eat leafy green vegetables we consume significant amounts of SQ sugars, which are used as an energy source by good gut bacteria," he said.
"Bacteria in the gut, such as crucial protective strains of E. coli, use SQ as a source of energy. E. coli provides a protective barrier that prevents growth and colonization by bad bacteria, because the good bugs are taking up all the habitable real estate," Dr Goddard-Borger said.
"E. coli is a key bacterial colonizer needed by our gut. We speculate that consumption of this specific molecule within leafy greens will prove to be an important factor in improving and maintaining healthy gut bacteria and good digestive health," he added.
Professor Williams said the team had revealed how bacteria extract the sugar from plants in order to fuel their growth.
"We discovered the enzyme YihQ, which is used by bacteria to absorb and metabolize these sulfur-containing sugars as food. Sulfur is critical for building proteins, the essential components of all living organisms. SQ is the only sugar molecule which contains sulfur, and 'digestion' of the molecule by bacteria releases sulfur into the environment, where it re-enters the global 'sulfur cycle' to be reused by other organisms," he said.
Professor Williams said that the pathway was unusual, but abundant in biological organisms.
"This work answers a 50-year mystery that has surrounded how sulfur - an element essential for life on Earth - was used and recycled by living organisms. What is remarkable is that the YihQ enzyme was hiding in plain sight and is produced by the humble bacterium E. coli, present in nearly every biologist's laboratory," he said.
The discovery also provides crucial insights that may one day be exploited to develop an entirely new class of antibiotics.
Dr Goddard-Borger said, "New antimicrobial strategies are desperately needed as more and more bacteria acquire resistance to existing classes of antibiotics. We think it will be possible to use these widespread enzymes to enable highly specific delivery of antibiotics to harmful forms of E. coli and other pathogens, such as Salmonella, responsible for food poisoning, while leaving the good gut bacteria untouched."