1J: Effect of Brominated Indole-3-carboxaldehydes on the Communication and Biofilm Formation in Bacteria

Abstract

Quorum sensing (QS) is a type of intercellular communication used by many bacterial species wherein bacteria produce and secrete signaling molecules to affect changes in bacterial populations. As the population of bacteria grows, the concentration of signaling molecules secreted also increases in the environment. Once the signaling molecules reach a threshold concentration, the molecules saturate their respective receptors on, or in, the bacteria altering gene expression.

Indole is an organic compound that serves to mediate communication among many bacteria and it has been shown to affect a wide variety of bacterial behaviors including biofilm formation, antibiotic resistance, and the production of virulence factors. Therefore, targeting indole signaling may be a way to mediate pathogenicity among bacteria without the use of traditional antibiotics. In this study, we used a model bacterium Chromobacterium violaceum to investigate a subset of indole derivatives, and we identify three new quorum sensing inhibitors: 5, 6, and 7-bromoindole-3-carboxaldehydes. We further show that bromination of indole-3-carboxaldehyde significantly increased the potency of quorum sensing inhibition. In addition, we evaluated the impact of those molecules on biofilm formation in the pathogenic species Pseudomonas aeruginosa.