Interkingdom communication 2.0: pheromone-based control between Bacillus subtilis and Saccharomyces cerevisiae

Microbial communities found in nature are complex and thrive in harmony, consisting of organisms derived from several kingdoms. Hence, they need to be able to communicate by quorum-sensing molecules to co-exist in close proximity. Being able to engineer artificial interkingdom communication for biotechnological approaches, such as degradation of complex biomaterials in one fermenter using controlled signaling between microorganisms, would be beneficial. Therefore, we wanted to establish a proof of principle by enabling the Gram-positive bacterium Bacillus subtilis to communicate in a controlled manner with the eukaryotic yeast Saccharomyces cerevisiae by exploiting the yeast's pheromone system. We genetically modified B. subtilis to heterologously produce the α-pheromone after bacitracin induction, which in turn would activate the production of the green fluorescent protein mNeongreen upon pheromone recognition by S. cerevisiae. Co-cultivation in modified growth medium and induction of pheromone expression was successful and repeatable. Yeast activation and production of mNeongreen was visible not only by analysis but also by epifluorescence microscopy of the co-culture. This study successfully demonstrated controlled interkingdom signaling between microorganisms by leveraging their native communication systems. KEY POINTS: • Heterologous production and secretion of small peptides in Bacillus subtilis. • Interkingdom communication between bacteria and yeast. • Signaling by artificially produced pheromones.