Quorum sensing inhibition evaluation method: An experiment‐based microbiology laboratory course

Bacteria have developed a cell-to-cell communication system called quorum sensing (QS), allowing them to regulate group behavior and synchronize the expression of virulence factors, responsible for increasing their infection capacity and resistance to antimicrobials. Although the control of microbial infections through the inhibition of microbial growth has traditionally been the basis of antimicrobial chemotherapy, the emergence of antimicrobial resistance has led to the search for new microbial control strategies, namely through the inhibition of QS. Among the agents studied to inhibit this bacterial communication are essential oils (EO), which are considered very effective QS inhibitors. When searching for new QS inhibitor agents, it is essential to have a cheap and easy-to-perform method that allows the evaluation of this activity. Chromobacterium violaceum is a Gram-negative bacterium that has been widely used as a model organism in QS research laboratories because it produces the violet-colored pigment violacein, which is regulated by QS and is an easily observable and quantifiable characteristic marker. The objective of this work is to describe a method to evaluate the inhibition of the QS using Cymbopogon martinii EO as a potential inhibitory agent for violacein production by C. violaceum, which can be applied in the Microbiology laboratory course as a part of the programs of several science degrees. The proposed method is inexpensive and does not require specific equipment, enabling its easy implementation by the laboratory team and professors.