Abstract
Quorum sensing networks have been identified in over one hundred bacterial species to date. A subset of these networks regulate group behaviors, such as bioluminescence, virulence, and biofilm formation, by sending and receiving small molecules called homoserine lactones (HSLs). Bioengineers have incorporated quorum sensing pathways into genetic circuits to connect logical operations. However, the development of higher-order genetic circuitry is inhibited by crosstalk, in which one quorum sensing network responds to HSLs produced by a different network. Here, we report the construction and characterization of a library of ten synthases including some that are expected to produce HSLs that are incompatible with the Lux pathway, and therefore show no crosstalk. We demonstrated their function in a common lab chassis, Escherichia coli BL21, and in two contexts, liquid and solid agar cultures, using decoupled Sender and Receiver pathways. We observed weak or strong stimulation of a Lux receiver by longer-chain or shorter-chain HSL-generating Senders, respectively. We also considered the under-investigated risk of unintentional release of incompletely deactivated HSLs in biological waste. We found that HSL-enriched media treated with bleach were still bioactive, while autoclaving deactivates LuxR induction. This work represents the most extensive comparison of quorum signaling synthases to date and greatly expands the bacterial signaling toolkit while recommending practices for disposal based on empirical, quantitative evidence.
Highlights
Quorum sensing networks enable bacteria to monitor and respond to changes in their population density by coupling gene regulation with diffusible chemical signals from neighboring bacteria [1]
Transgenic homoserine lactones (HSLs) synthases in E. coli, the Western Alliance to Expand Student Opportunities (WAESO, NSF HRD 1401190, https://mge-p1000.asu.edu/waeso/), the School of Molecular Sciences at Arizona State University, and the School of Biological and Health Systems Engineering at Arizona State University for their support of the undergraduate co-authors
We considered the length of the acyl chain, the chain saturation, and the number of different HSLs produced by a single synthase
Summary
Quorum sensing networks enable bacteria to monitor and respond to changes in their population density by coupling gene regulation with diffusible chemical signals from neighboring bacteria [1]. These signaling networks control group behaviors such as virulence, biofilm. Transgenic HSL synthases in E. coli (http://igem.org), the Western Alliance to Expand Student Opportunities (WAESO, NSF HRD 1401190, https://mge-p1000.asu.edu/waeso/), the School of Molecular Sciences at Arizona State University, and the School of Biological and Health Systems Engineering at Arizona State University for their support of the undergraduate co-authors.
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