Abstract
Quorum sensing (QS) systems play important roles in regulating many physiological functions of microorganisms, such as biofilm formation, bioluminescence, and antibiotic production. One marine algicidal bacterium, Ponticoccus sp. PD-2, was isolated from the microalga Prorocentrum donghaiense, and its N-acyl-homoserine lactone (AHL)-mediated QS system was verified. In this study, we analyzed the AHLs profile of strain PD-2. Two AHLs, 3-oxo-C8-HSL and 3-oxo-C10-HSL, were detected using a biosensor overlay assay and GC–MS methods. Two complete AHL-QS systems (designated zlaI/R and zlbI/R) were identified in the genome of strain PD-2. When expressed in Escherichia coli, both zlaI and zlbI genes could each produce 3-oxo-C8-HSL and 3-oxo-C10-HSL. Algicidal activity was investigated by evaluating the inhibitory rate (IR) of microalgae growth by measuring the fluorescence of viable cells. We found that the metabolites of strain PD-2 had algicidal activity against its host P. donghaiense (IR 84.81%) and two other red tide microalgae, Phaeocystis globosa (IR 78.91%) and Alexandrium tamarense (IR 67.14%). β-cyclodextrin which binds to AHLs and inhibits the QS system reduced the algicidal activity more than 50%. This indicates that inhibiting the QS system may affect the algicidal metabolites production of strain PD-2. Our study indicated that a QS-regulated algicidal system may play a potential role in the process of red tides disintegration. QS might be a potential way to control red tides.
Highlights
Quorum sensing (QS) is a cell density-dependent system for information transfer among bacteria
The most studied intercellular AI molecules are N-acyl-homoserine lactones (AHLs), which can be detected by biosensors, gas chromatography–mass spectrometer (GC–MS), and high-performance liquid
Analysis of the AHL profile Bioautography analysis thin-layer chromatography (TLC) overlay assay with the biosensor KYC55 suggested that strain PD-2 produced two AHLs (Fig. 1)
Summary
Quorum sensing (QS) is a cell density-dependent system for information transfer among bacteria. It enables the bacterial cells to sense changes in cell density through the concentration of signal molecules called autoinducers (AI) released by bacteria themselves (Guo et al 2011). When the bacteria grow to a high cell density, the concentration of AI could reach a threshold and bind to a receptor protein. Chi et al AMB Expr (2017) 7:59 chromatography-mass spectrometer (HPLC-MS) (Li et al 2015). These AHLs are generated by an autoinducer synthase, the product of a luxI type gene, and the receptor is a cognate luxR type protein. It is necessary to determine the profiles of AHLs produced by different luxI homologs to better understand the QS system
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