Order of authorship in the original publication: Piewngam, Zheng, Nguygen....The authors discovered a mechanism by which probiotics help maintain a healthy microbiome. They showed that Bacillus subtilis can produce a bioactive lipopeptide called Fengycin that inhibits quorum sensing of pathogens-- a vital signaling mechanism of some bacteria, which helps them regulate gene transcription. Quorum sensing is tied to and responsive to the population density of that bacteria. In this study the Bacillus fengycin eradicated Staphylococcus aureus. 

(Thanks to Juan Weiss for this reference and its interpretation.)