Mecanismos de inhibición de quorum sensing: estudio en la microbiota de invertebrados marinos y análisis in silico en el medio ambiente

Abstract

Quorum sensing (QS) bacterial communication controls the production of virulence factors in numerous pathogenic species, thus regulating the development of different bacterial infectious diseases. These systems are characterized by the production and detection of autoinducers, which is cell-density dependent. Once a threshold concentration is reached, autoinducers regulate target gene expression in many microorganisms. Interest in understanding QS systems has been increasing in the last few years, due in part of the development of bacterial resistances to antibiotics that are used in the tratement of bacterial infections. Therefore, QS inhibition is a novel and eco-friendly alternative in the fight against such infections. QS interruption would imply the inhibition or attenuation of the pathogens virulence without affecting their growth, thus provoking less resistances. In this work, QS disruption mechanisms in the microbiota of marine invertebrates have been studied. Marine invertebrate symbiotic microorganisms are considered to be an underexplored source of new bioactive molecules. Among them, 23 strains belonging to the genus Vibrio were selected for their ability to interfere with QS following a nonenzymatic mechanism (QSI). One of them stood out for the production of tyramine and N-acetyltyramine, the compounds responsible of its QSI activity. Secondly, 21 strains were selected for their ability of producing N-acylhomserin lactone (AHL)-degrading enzymes, called Quorum Quenching (QQ) enzymes. The inhibition mechanisms were characterized, highlighting the abundance of acylase-like enzymes. Moreover, the potential use of QQ enzymes in the reduction of the virulence of pathogens through in vitro and in vivo assays was evaluated. Given the increasing importance of QQ inhibition mechanisms, bioinformatics and metagenomics have also been used to determine the QQ enzyme abundance in numerous environments from very diverse origins, using free access metagenomes The abundance of QQ systems in different environments has veen demonstrated, confirming that lactonases are usually more abundant than acylases. Lastly, the active site responsible of the QQ activity was found in the HqiA isochorismatase with lactonase activity, a new enzyme found by our research group in a previous work. This information has been used to identify for the first time the QQ activity in a group of isochorismatases in other bacteria. To sum up, this Doctoral Thesis covers the study of QS inhibition systems from different points of view, demonstrating the importance of them and its potential biotechnological application.