Selection of the N-Acylhomoserine Lactone-Degrading Bacterium Alteromonas stellipolaris PQQ-42 and of Its Potential for Biocontrol in Aquaculture

Abstract

The production of virulence factors by many pathogenic microorganisms depends on the intercellular communication system called quorum sensing, which involves the production and release of signal molecules known as autoinducers. Based on this, new-therapeutic strategies have emerged for the treatment of a variety of infections, such as the enzymatic degradation of signaling molecules, known as quorum quenching (QQ). In this study, we present the screening of QQ activity amongst 450 strains isolated from a bivalve hatchery in Granada (Spain), and the selection of the strain PQQ-42, which degrades a wide range of N-acylhomoserine lactones (AHLs). The selected strain, identified as Alteromonas stellipolaris, degraded the accumulation of AHLs and reduced the production of protease and chitinase and swimming motility of a Vibrio species in co-cultivation experiments in vitro. In the bio-control experiment, strain PQQ-42 significantly reduced the pathogenicity of Vibrio mediterranei VibC-Oc-097 upon the coral Oculina patagonica showing a lower degree of tissue damage (29.25 ± 14.63%) in its presence, compared to when the coral was infected with V. mediterranei VibC-Oc-097 alone (77.53 ± 13.22%). Our results suggest that this AHL-degrading bacterium may have biotechnological applications in aquaculture.

Silencing of Phytopathogen Communication by the Halotolerant PGPR Staphylococcus Equorum Strain EN21

“…QQ activity of Staphylococcus sp. strain EN21 for AHL degradation was analysed using a well diffusion agar-plate assay [42,43]. Briefly, each synthetic AHL in a final concentration of 25 µM was added to overnight cultures of strain EN21 and then incubated at 28 • C for 24 h. Cell-free TSB medium supplemented with the same concentration of AHLs was incubated as negative control.…”

“…Co-culture assays of plant bacterial pathogens and strain EN21 were carried out according to the methodology described by Torres et al [43]. Briefly, 10 9 CFU mL −1 of each pathogenic strain was co-cultured with 10 9 CFU mL −1 of strain EN21 (1:100) in TSB medium at 28 • C and 150 rpm for 24 h. A similar concentration of each pathogen was added to cell-free TSB medium as negative control.…”

High Prevalence of Quorum-Sensing and Quorum-Quenching Activity among Cultivable Bacteria and Metagenomic Sequences in the Mediterranean Sea

“…The pioneer studies on the ecological relevance of QQ processes carried out with bacteria isolated from soil and rhizosphere indicated that 2–4.8% of these strains had the ability to interfere with AHLs [ 42 , 43 , 44 ]. More recent studies revealed a high prevalence of QQ enzymes in the marine environment: enzymatic QQ activity was observed in bacterial strains isolated from corals [ 23 , 45 ], sponges [ 46 ], marine biofilms [ 47 ], estuarine and open ocean superficial seawater [ 48 , 49 ], and fish and bivalve hatcheries [ 50 , 51 ], presenting higher frequencies of bacteria with this capability (2–46%) in comparison to terrestrial samples [ 46 , 48 , 52 , 53 , 54 ]. The importance of QQ processes in the marine environment was further supported by metagenomic studies showing a high frequency of QQ enzymes in marine metagenomic collections including the Global Ocean Sampling collection [ 48 ].…”

Quorum Quenching Properties and Probiotic Potentials of Intestinal Associated Bacteria in Asian Sea Bass Lates calcarifer

“…Application of AHL degrading bacteria able to utilize AHL molecules of marine and freshwater pathogens as a food source is a developing idea due to their previously successful outcomes [17][18][19][20][21][22]. However, the majority of the strains that have been tested in the past are allochthonous QQ bacteria [21,23].…”

“…Application of AHL degrading bacteria able to utilize AHL molecules of marine and freshwater pathogens as a food source is a developing idea due to their previously successful outcomes [17][18][19][20][21][22]. However, the majority of the strains that have been tested in the past are allochthonous QQ bacteria [21,23]. Moreover, the isolation of autochthonous bacteria with QQ potential has frequently been reported from freshwater fish [19,[24][25][26], and to our knowledge, there is only one report in marine fish [27].…”