Quorum sensing inhibition activity of marine Gammaproteobacteria

Abstract Quorum sensing (QS) is a communication mechanism between bacteria, mediated by signals released at high cell densities, which regulates bioluminescence, virulence, and biofilm formation. By inhibiting QS, these processes can be controlled when they become undesirable, as in infectious diseases and during biodeterioration of materials. In this context, this study investigated the Quorum Sensing Inhibition (QSI) activity in 60 strains of marine Gammaproteobacteria isolated from samples of the South Atlantic Ocean. Initially, the bacterial strains were screened using plaque assays, with Chromobacterium violaceum LAMA 0447 and Serratia marcescens LAMA 1170 as indicator strains. Subsequently, seven selected bacteria were further evaluated via luminescence test with Aliivibrio fischeri, considering both cultivation time and mixed cultures with A. fischeri. Later, three strains were investigated regarding the chemical nature of their substances with QSI activity via ultrafiltration and proteinase K treatments. Finally, the genome of one of these strains was examined for the identification of genes related to QSI activity. In total, 16 strains exhibited QSI activity in plaque assays, and the activity of seven of these strains was further assessed in quantitative assays. Higher activity was observed in supernatants obtained after 48 hours of cultivation for six strains and from mixed cultures with A. fischeri. Treated supernatants of three strains allowed us to infer that, for Halomonas olivaria LAMA 0626, the substances responsible for QSI are probably enzymes. For the other two strains, belonging to the Marinobacter genus, more than one type of substance seems to be involved: (1) at least one enzyme and (2) non-protein low molecular weight molecules (< 10 kDa). Genes identified in M. excellens LAMA 0842 support this hypothesis. In summary, marine bacteria from the Gammaproteobacteria class can disrupt the communication of other bacteria, which could form the basis for the development of novel microbial control products.