Determination of Whether Quorum Quenching Is a Common Activity in Marine Bacteria by Analysis of Cultivable Bacteria and Metagenomic Sequences

Abstract

The abundance of quorum quenching (QQ) activity was evaluated in cultivable bacteria obtained from oceanic and estuarine seawater and compared with the frequency of QQ enzyme sequences in the available marine metagenomic collections. The possible role of the high QQ activity found among marine bacteria is discussed. The low bacterial population encountered in the open sea and the low chemical stability of N-acyl-homoserine lactones (AHLs) in seawater have led to the suggestion that the AHL-mediated quorum sensing (QS) activity may be concentrated in specific microhabitats in the marine environment (3, 11) and that, therefore, the quorum quenching (QQ) processes would be expected to be less frequent in seawater. The presence of AHLs in marine particulate organic carbon has been recently confirmed, with more than 10% of the particle-associated bacteria being identified as AHL producers (10). Even higher QS activity values have been found for isolates from subtidal biofilms (31% [12]) and sponges (20 to 56% [14]), while a similar value was found for marine snow and microalgal isolates (9.3% [9]). Moreover, the addition of exogenous AHLs to incubations containing marine organic particles stimulated the activity of some key hydrolytic enzymes, suggesting a role of QS signals in the regulation of the degradation of particulate organic carbon (10). In a recent work, the importance of QQ processes in marine dense microbial communities was evidenced by the large amount of cultivable marine bacteria active against AHL signals that could be isolated from marine habitats such as sediments, biofilms, and the surface of the alga Fucus vesiculosus (18). These results indicate that QQ could be a usual strategy adopted in the marine environment to achieve competitive advantages at least in surfaces such as biofilms and eukaryotic niches. As an approximation to evaluate the ecological significance of QQ processes in the marine environment and to elucidate if QQ processes are as abundant in marine seawater pelagic microbial communities as previously described for coastal dense communities (18), we studied the presence of QQ activity among isolates from estuarine and open-ocean seawater. This activity was compared with the frequency of sequences homologous to known QQ enzymes in the available long-read marine metagenomic collections.Quorum quenching activity among cultivable bacteria. In order to evaluate if QQ processes are as abundant among cultivable bacteria from marine seawater pelagic microbial communities as previously described for those isolated from marine surfaceassociated communities (18), 464 marine isolates were obtained from three different seawater samples using different culture media and temperatures and screened for detection of AHL-QQ activity using a bioassay based on Chromobacterium violaceum reporter strains as previously described (18). One of the samples was obtained from surface water at 10 m from the shore line in an estuary (42°0.33=0.45.32ЉN, 8°0.53=0.08.23ЉW, Spain), and the other two samples were obta...

Novel Reporter for Identification of Interference with Acyl Homoserine Lactone and Autoinducer-2 Quorum Sensing

“…Our finding of unusually high frequencies of bacteria with significant QS-interfering activities within marine consortia is in accordance with recent reports on the occurrence of marine bacteria with AHL-QQ activities in pelagic and marine surface-associated communities (17,105). Using C. violaceum CV026 (85, 86) (see above) as a reporter strain, Romero et al (105) demonstrated that 24 out of 166 cultivable bacterial strains isolated from different marine microbial communities eliminated or significantly reduced AHLs, a significantly higher percentage than that reported for soil isolates (106,107).…”

“…Using C. violaceum CV026 (85, 86) (see above) as a reporter strain, Romero et al (105) demonstrated that 24 out of 166 cultivable bacterial strains isolated from different marine microbial communities eliminated or significantly reduced AHLs, a significantly higher percentage than that reported for soil isolates (106,107). Moreover, analysis of marine metagenomes revealed a high occurrence of genes encoding lactonases and acylases (17), both known to interfere with AHL QS. These findings reinforce the potential ecological role of the QS and QQ processes in marine environments, particularly in dense microbial communities on biological surfaces and particles.…”

“…One example is a V. harveyi-based reporter system with a mutated autoinducer synthase (LuxS) that can be used to detect external accumulation of AI-2, leading to bioluminescence (67). A second reporter system is based on lacZ fusion to the E. coli AI-2-inducible promoter lsrA (11,17). The current knowledge of QS interference mechanisms for the different QS processes in Gramnegative and Gram-positive bacteria, as well as the establishment of different reporter systems, is summarized in a recent review by LaSarre and Federle (19), who also discuss the potential use of QS inhibition for the control of bacterial pathogenicity.…”

“…Because biofilms potentially have harmful effects on living organisms (in the case of pathogenic bacteria) and on yields in the industrial sector, an attractive novel strategy to control biofilm formation based on QS interference (quorum quenching [QQ]) has been proposed and established (12)(13)(14)(15)(16)(17)(18)(19). Synthesis of QS-interfering compounds has been demonstrated for bacteria and eukaryotes (20)(21)(22)(23)(24), leading to the hypothesis that eukaryotes have evolved such defense mechanisms as a strategy for protection and inhibition of association with bacterial pathogens (25).…”

MomL, a Novel Marine-Derived N -Acyl Homoserine Lactonase from Muricauda olearia

“…Most of these QQ bacteria were isolated from the marine environment (14)(15)(16)(17), and only one was derived from soil (the potato root-associated Chryseobacterium sp. strain StRB126) (18).…”