Quantifying the Integration of Quorum-Sensing Signals with Single-Cell Resolution

Department of Physics, Princeton University, Princeton, NJ, USA.
PLoS Biology (Impact Factor: 9.34). 04/2009; 7(3):e68. DOI: 10.1371/journal.pbio.1000068
Source: PubMed


Author Summary

Although bacteria are unicellular, the individual cells communicate with each other via small diffusible molecules. This communication process, known as quorum sensing, allows groups of bacteria to track the density of the population they are in, synchronize gene expression across the population, and thereby carry out collective activities similar to those of cells in multi-cellular organisms. Many bacterial species use multiple signaling molecules, but it remains a mystery why multiple signals are required and how the information encoded in them is integrated by bacteria. To explore these questions, we studied a model quorum-sensing bacterium Vibrio harveyi. Using single-cell fluorescence microscopy, we quantified quorum-sensing responses and analyzed the mechanism of integration of multiple signals. Surprisingly, we found that information from two distinct signals is combined strictly additively, with precisely equal weight from each signal. Our results revealed a coherent response across the population with little cell-to-cell variation, allowing the entire population of bacterial cells to reliably distinguish multiple environmental states. We argue that multiple signals and multiple response states could be used to distinguish distinct stages in the development of a bacterial community.

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    • "Detection of AI-2 Activity AI-2 activity was measured as previously described (Taga and Xavier, 2011) using the V. harveyi AI-2 reporter strain TL26 (DluxN DluxS DcqsS; Long et al., 2009). To determine AI-2 activity in mouse cecal extracts, the cecal contents were homogenized at a 10% weight/volume concentration in 0.1 M MOPS (pH 7). "
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    ABSTRACT: The mammalian gut microbiota harbors a diverse ecosystem where hundreds of bacterial species interact with each other and their host. Given that bacteria use signals to communicate and regulate group behaviors (quorum sensing), we asked whether such communication between different commensal species can influence the interactions occurring in this environment. We engineered the enteric bacterium, Escherichia coli, to manipulate the levels of the interspecies quorum sensing signal, autoinducer-2 (AI-2), in the mouse intestine and investigated the effect upon antibiotic-induced gut microbiota dysbiosis. E. coli that increased intestinal AI-2 levels altered the composition of the antibiotic-treated gut microbiota, favoring the expansion of the Firmicutes phylum. This significantly increased the Firmicutes/Bacteroidetes ratio, to oppose the strong effect of the antibiotic, which had almost cleared the Firmicutes. This demonstrates that AI-2 levels influence the abundance of the major phyla of the gut microbiota, the balance of which is known to influence human health. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Cell Reports 03/2015; 10(11). DOI:10.1016/j.celrep.2015.02.049 · 8.36 Impact Factor
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    • "To test the predictions of the model, we constructed three V. harveyi strains that report on target mRNA levels by integrating a luxR, a luxM, or a luxO 5 0 UTR translational GFP fusion under a constitutive promoter onto the chromosome. We used mCherry oriented in the opposite direction to normalize for cellular protein (Long et al., 2009). We measured GFP and mCherry fluorescence after we induced Qrr production by adding a quorum-sensing antagonist (see Experimental Procedures) (Shao et al., 2013). "
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    ABSTRACT: Quorum sensing is a cell-cell communication process that bacteria use to transition between individual and social lifestyles. In vibrios, homologous small RNAs called the Qrr sRNAs function at the center of quorum-sensing pathways. The Qrr sRNAs regulate multiple mRNA targets including those encoding the quorum-sensing regulatory components luxR, luxO, luxM, and aphA. We show that a representative Qrr, Qrr3, uses four distinct mechanisms to control its particular targets: the Qrr3 sRNA represses luxR through catalytic degradation, represses luxM through coupled degradation, represses luxO through sequestration, and activates aphA by revealing the ribosome binding site while the sRNA itself is degraded. Qrr3 forms different base-pairing interactions with each mRNA target, and the particular pairing strategy determines which regulatory mechanism occurs. Combined mathematical modeling and experiments show that the specific Qrr regulatory mechanism employed governs the potency, dynamics, and competition of target mRNA regulation, which in turn, defines the overall quorum-sensing response. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell 01/2015; 160(1-2):228-240. DOI:10.1016/j.cell.2014.11.051 · 32.24 Impact Factor
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    • "V. harveyi DluxM DluxPQ DcqsS strain (TL25) was grown in the presence of 1 mM AI-1 to mid-logarithmic phase. DMSO (white bars) or 100 mM 3-oxo-C12-HSL (black bars) was added to the culture (Long et al, 2009). (A) Samples were collected 15 min after the addition of 3-oxo-C12-HSL and the mRNA levels of the target genes were measured by qRT– PCR. "
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    ABSTRACT: Quorum sensing is a chemical communication process that bacteria use to control collective behaviours including bioluminescence, biofilm formation, and virulence factor production. In Vibrio harveyi, five homologous small RNAs (sRNAs) called Qrr1-5, control quorum-sensing transitions. Here, we identify 16 new targets of the Qrr sRNAs. Mutagenesis reveals that particular sequence differences among the Qrr sRNAs determine their target specificities. Modelling coupled with biochemical and genetic analyses show that all five of the Qrr sRNAs possess four stem-loops: the first stem-loop is crucial for base pairing with a subset of targets. This stem-loop also protects the Qrr sRNAs from RNase E-mediated degradation. The second stem-loop contains conserved sequences required for base pairing with the majority of the target mRNAs. The third stem-loop plays an accessory role in base pairing and stability. The fourth stem-loop functions as a rho-independent terminator. In the quorum-sensing regulon, Qrr sRNAs-controlled genes are the most rapid to respond to quorum-sensing autoinducers. The Qrr sRNAs are conserved throughout vibrios, thus insights from this work could apply generally to Vibrio quorum sensing.
    The EMBO Journal 07/2013; 32(15). DOI:10.1038/emboj.2013.155 · 10.43 Impact Factor
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