Wolbachia bacteria let vitamin B2-deficient yeast grow without added vitamin B2

Infected yeast strains missing key riboflavin-synthesis genes grew without the vitamin and showed slightly higher survival under two stresses.

Editorial illustration — not from the study.

Researchers tested two Saccharomyces cerevisiae strains with deletions in RIB1 or RIB4, genes involved in making riboflavin. Without added riboflavin, both strains failed to grow, making them riboflavin-dependent strains.

After infection with the Wolbachia strain wStr, both yeast strains no longer showed this dependency. The infection also produced a mild increase in survival after exposure to 1 M sodium chloride or 10 mM hydrogen peroxide. The researchers propose this artificial yeast–bacterium system as a way to study harmful, optional and beneficial relationships between hosts and internal symbionts.

What the infected yeast did

The two yeast mutants, called ΔRIB1 and ΔRIB4, could not grow without externally supplied riboflavin. Wolbachia wStr infection cured this riboflavin dependency in both mutants, allowing them to grow without added riboflavin. Infected yeast also showed mildly improved survival after exposure to 1 M NaCl or 10 mM hydrogen peroxide. The abstract does not establish how Wolbachia restored growth in the mutants.

Why this model matters

The result creates an unusual experimental system in which a bacterium living inside yeast compensates for a defect in the yeast’s riboflavin pathway. Because the system uses defined yeast mutants and Wolbachia infection, it may help researchers examine how internal microbes can have harmful, optional or beneficial effects on their hosts.

Evidence and caveats

This is an experimental study using two engineered Saccharomyces cerevisiae mutants and Wolbachia wStr infection. The abstract does not provide sample sizes, effect sizes or details of the experiments, and it does not identify the mechanism behind the restored growth. The model is artificial, so its results may not represent naturally occurring yeast–Wolbachia relationships or interactions in other organisms.

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