The dynamic response of quorum sensing to density is robust to signal supplementation and individual signal synthase knockouts
Quorum sensing (QS) is a widespread mechanism of environment sensing and behavioural coordination in bacteria. At its core, QS is based on the production, sensing and response to small signalling molecules. Previous work with shows that QS can be used to achieve resolution and deliver a dosed respon...
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Veröffentlicht in: | Microbiology (Society for General Microbiology) 2023-05, Vol.169 (5) |
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Zusammenfassung: | Quorum sensing (QS) is a widespread mechanism of environment sensing and behavioural coordination in bacteria. At its core, QS is based on the production, sensing and response to small signalling molecules. Previous work with
shows that QS can be used to achieve
resolution and deliver a dosed response to the bacteria's density environment, implying a sophisticated mechanism of control. To shed light on how the mechanistic signal components contribute to graded responses to density, we assess the impact of genetic (AHL signal synthase deletion) and/or signal supplementation (exogenous AHL addition) perturbations on
reaction-norms to changes in density. Our approach condenses data from 2000 timeseries (over 74 000 individual observations) into a comprehensive view of QS-controlled gene expression across variation in genetic, environmental and signal determinants of
expression. We first confirm that deleting either (∆
) or both (∆
) AHL signal synthase gene attenuates QS response to density. In the
background we show persistent yet attenuated density-dependent
expression due to native 3-oxo-C12-HSL signalling. We then test if density-
quantities of AHL signal (3-oxo-C12-HSL, C4-HSL) added to the WT either flatten or increase responsiveness to density and find that the WT response is robust to all tested concentrations of signal, alone or in combination. We then move to progressively supplementing the genetic knockouts and find that cognate signal supplementation of a single AHL signal (∆
+3-oxo-C12-HSL, ∆
+C4HSL) is sufficient to restore the ability to respond in a density-dependent manner to increasing density. We also find that dual signal supplementation of the double AHL synthase knockout restores the ability to produce a graded response to increasing density, despite adding a density-
amount of signal. Only the addition of high concentrations of both AHLs and PQS can force maximal
expression and ablate responsiveness to density. Our results show that density-dependent control of
expression is robust to multiple combinations of QS gene deletion and density-independent signal supplementation. Our work develops a modular approach to query the robustness and mechanistic bases of the central environmental
phenotype of quorum sensing. |
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ISSN: | 1465-2080 1350-0872 1465-2080 |
DOI: | 10.1099/mic.0.001321 |