Evidencing microbial communication through Quorum Sensing systems in the environment: a practical approach for undergraduate students

Abstract

In the environment, communication among microorganisms is a key aspect of their lives. Through communication, single cells of a microbial population can coordinate their gene expression and, in consequence, their physiology. Quorum sensing systems (QS) are one of these mechanisms that allow this communication through the production and detection of signal molecules whose concentration is related to the density of the signaling cells. In several Gram-negative bacteria, these QS signals belongs to the N-acyl homoserine lactone (AHL) family, which can be detected in the laboratory by means of simple bioassays. In this report, we present for undergraduate students a detailed protocol that allows to evidence QS activity in environmental samples. First, with a selective culture medium, Gram-negative bacteria are isolated from samples provided by the students. Then, isolates are screened with two biosensor strains for the detection of AHL production. Positive results are visualized by the induction of violacein production in the biosensors. These experiments evidence the presence of communicating microorganisms in the analyzed samples. This simple protocol allows the students to analyze a particular microbial activity in samples provided by them, which enhance their learning experiences.