A Yeast-Derived Metabolite from Kefir: Promising Research in the Fight Against Pathogens and Excessive Inflammation

Researchers at Ben-Gurion University in Israel are working on isolating specific molecules from kefir that can combat pathogenic bacteria and treat inflammatory bowl disease, as well as halt cytokine storms such as seen in severe cases of COVID.[i]  For those unfamiliar with kefir, it is a  probiotic milk product, typically fermented with  lactic acid-producing bacteria and yeasts.  Kefir is well-known to have health benefits for humans, and has long been thought to potentially be capable of protecting against bacterial infections.  The mechanism, however, has not been fully understood.  These researchers wanted to isolate the specific molecules in kefir that can combat bacterial infections and modulate inflammation.

The scientists analyzed the microbiome of kefir: this revealed a predominance (70%) of a fungus called Kluyveromyces marxianus. The kefir also contained 24% Lactobacillus species, and the rest was comprised of other bacterial types. They discovered a new fungus-secreted metabolite which they called tryptophol acetate which appears to inhibit bacterial communication and virulence by blocking something called “quorum sensing” (QS) of several kinds of bacteria. QS is a process of cell-to-cell communication which bacteria use to adjust gene expression.  For years, this has been researched as a means of controlling the virulence of infection by pathogens.[ii]  In this paper, the authors state that QS plays a “…major role in the synchronized production of virulence factors..,” and thus, “…significant efforts have been directed in recent years towards development of anti-bacterial therapeutic strategies based upon identification of antagonists or agonists in QS cascades…”

Thus far, these scientists have been able to demonstrate that this metabolite can reduce the virulence of the bacterium Vibrio cholerae, which causes cholera:  “These results are notable, since this is the first demonstration that QS in human pathogenic bacteria can be modulated by molecules secreted by probiotic yeast.”  Disrupting bacterial communication is also a promising way of treating antibiotic-resistant bacteria.  They have also demonstrated these the molecules are highly anti-inflammatory, and in a mouse model, healed mice who were subjected to a cytokine storm (a barrage of inflammatory chemicals in the body) such as has proven the main cause of death in those with severe COVID.  The metabolite also restored balance to the immune system.

The scientists conclude that this fungus-derived novel compound, tryptophol acetate, can interfere in pathogenic bacteria’s quorum sensing and thus, “…may play important roles in enabling microorganism co-existence in multi-population environments, such as probiotic foods and the gut microbiome. This discovery may account for anti-virulence properties of the human microbiome and could aid elucidating health benefits of probiotic products against bacterially associated diseases.”

For now, maybe we should be adding kefir regularly to our diets!


[i] Orit Malka et al, Cross-kingdom inhibition of bacterial virulence and communication by probiotic yeast metabolites, Microbiome (2021). DOI: 10.1186/s40168-021-01027-8

[ii] Rutherford ST, Bassler BL. Bacterial quorum sensing: its role in virulence and possibilities for its control. Cold Spring Harb Perspect Med. 2012;2(11):a012427. Published 2012 Nov 1. doi:10.1101/cshperspect.a012427

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