Researchers at Shinshu University in Japan have developed a new strain of probiotic bacteria with enhanced properties using ribosome engineering. The team, led by Professor Takeshi Shimosato from the Institute for Aqua Regeneration at Shinshu University, introduced mutations into the protein synthesis mechanism of Lacticaseibacillus rhamnosus GG (LGG), a widely used probiotic. These genetic changes resulted in mutant strains that display altered surface proteins and increased levels of "moonlighting proteins," which are intracellular proteins that also function on the cell surface.
The study, published in Microbiology Spectrum on December 2, 2025, describes how these modified LGG mutants adhere more strongly to intestinal cells and trigger greater activation of immune cells compared to their wild-type counterparts. According to Prof. Shimosato, "There is a growing commercial and medical demand for probiotics that do more than just 'balance the gut'-we need strains that actively improve health outcomes. However, classical breeding methods are slow, and genetic engineering is often barred from food use." He added, "We were inspired by the success of RE in the pharmaceutical field. We hypothesized that this technology, which 'wakes up' latent capabilities in bacteria by altering their ribosomes, could be repurposed to supercharge lactic acid bacteria."
The research found that one particular mutant strain with a K56N mutation produced 23 distinct surface proteins—compared to only five found in wild-type LGG—and had significantly higher amounts of surface Glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Prof. Shimosato explained: "The K56N mutant displayed increased expression of the moonlighting protein Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) on its surface and showed enhanced adhesion to human colonic mucin via GAPDH-mediated binding." He continued: "The present study extends this investigation by exploring how the K56N mutation affects extracellular vesicle (EV) composition and host immune modulation."
When tested with HT-29 human intestinal cells, twice as many K56N mutant bacteria adhered compared to wild-type LGG. This suggests these mutants could remain longer in the gut and help displace harmful bacteria from intestinal surfaces.
In experiments involving mouse macrophage cultures, extracellular vesicles from K56N mutants induced much higher secretion of tumor necrosis factor α (TNF-α), an important chemical messenger for immune responses. Four different surface proteins from K56N mutants were found to increase TNF-α secretion; only one such protein was identified in wild-type LGG.
These results indicate that K56N mutants may serve as "super-probiotics" due to their improved ability to colonize the gut and stimulate immune responses. Such properties could benefit individuals whose digestive systems eliminate standard probiotics too quickly or be used for developing stronger probiotic foods or supplements.
Prof. Shimosato concluded: "As ribosome-engineered LGG mutants can be obtained easily and safely and exhibit enhanced robustness and functionality, they are promising probiotic candidates."
