Quorum Sensing versus Quenching Bacterial Isolates Obtained from MBR Plants Treating Leachates from Municipal Solid Waste.

Albert Soler,Cristina García-Vera,José Antonio Mendoza,Antonio Santos,Susana Serrano,Domingo Marquina,Cristina Álvarez,Andrea Muras,Lucía Arregui,Miguel Arroyo

doi:10.3390/ijerph15051019

Abstract

Quorum sensing (QS) is a mechanism dependent on bacterial density. This coordinated process is mediated by the synthesis and the secretion of signal molecules, called autoinducers (AIs). N-acyl-homoserine lactones (AHLs) are the most common AIs that are used by Gram-negative bacteria and are involved in biofilm formation. Quorum Quenching (QQ) is the interference of QS by producing hydrolyzing enzymes, among other strategies. The main objective of the present study was to identify QS and QQ strains from MBR wastewater treatment plants. A total of 99 strains were isolated from two Spanish plants that were intended to treat leachate from municipal solid waste. Five AHL producers were detected using AHL biosensor strains (Chromobacterium violaceum CV026 and Agrobacterium tumefaciens NT1). Fifteen strains of seventy-one Gram-positive were capable of eliminating or reducing at least one AHL activity. The analysis of 16S rRNA gene sequence showed the importance of the Pseudomonas genus in the production of biofilms and the relevance of the genus Bacillus in the disruption of the QS mechanism, in which the potential activity of lactonase or acylase enzymes was investigated with the aim to contribute to solve biofouling problems and to increase the useful lifespan of membranes.

Highlights

Microorganisms have developed complex communication systems to produce, and, in turn, respond to extracellular signals that are secreted by others [1,2,3]
A total of 99 bacterial strains (48 strains from WWTP-A and 51 from WWTP-B) were isolated from membrane bioreactors (MBR) activated sludge, with cellular densities that were ranging from 4.5 × 105 CFU mL−1 to
Comparison of the nearly complete 16S rRNA nucleotide sequences confirmed that the isolates belong to four different genera Bacillus, Gordonia, Pseudomonas, and Aeromonas, with a predominance of Bacillus cereus and Pseudomonas aeruginosa in all cases, similarity values among the isolated strains and the closest relative strains were between the 99% and the 100% (Table S1)

Summary

Introduction

Microorganisms have developed complex communication systems to produce, and, in turn, respond to extracellular signals that are secreted by others [1,2,3]. This microbial communication system, called Quorum Sensing (QS), is the ability to sense their population density through the synthesis and secretion of small molecules, called AutoInducers (AIs) [4,5,6]. Different types of signal molecules have been described [7], the best characterized QS signals are the N-acyl homoserine lactones (AHLs). Public Health 2018, 15, 1019; doi:10.3390/ijerph15051019 www.mdpi.com/journal/ijerph

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