Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication

Article abstract of DOI:10.1016/j.chempr.2019.03.005

External control of bacterial communication—quorum sensing—allows for the regulation of a multitude of biological processes. Herein, we describe the development of a new synthetic methodology, as well as the characterization, photoisomerization, and biological evaluation of a privileged series of novel photoswitchable quorum-sensing agonists and antagonists. The presented method allows for the rapid and convenient synthesis of previously unknown photoswitchable agonists with up to 70% quorum-sensing induction and inhibitors reaching up to 40% inhibition, which significantly extends the level of photocontrol over bacterial communication achieved before. Remarkably, for the lead photoswitchable agonist, a >700-fold difference in activity was observed between the irradiated and non-irradiated forms, which allows for antagonism-to-agonism switching upon exposure to light, showing levels of control unprecedented in photopharmacology. Finally, utilizing this system, we were able to regulate toxin production in Pseudomonas aeruginosa with light. Photopharmacology is an emerging approach aimed at the regulation of biological function with light. Herein, the application of molecular photoswitches allows for the reversible switching between two distinct structural states of bioactive compounds. Bacterial communication (quorum sensing) is an interesting target for photopharmacology, from the perspective of both clinical and basic research, because of its implications for pathogenicity of bacteria and complex biological mechanism of action. By the novel synthesis and application of photoswitchable modulators, we were able to reversibly control bacterial communication with light. Remarkably, one of our lead compounds allows the control of bacterial communication with very high selectivity, switching from a quorum-sensing inhibitor to a quorum-sensing activator upon irradiation with light, which was further exemplified by the control of quorum-sensing-regulated toxin production in Pseudomonas aeruginosa. By applying the photopharmacological approach, bacterial communication can be controlled with light through the application of photoswitchable modulators. Interestingly, one of the lead photoswitchable modulators of bacterial communication, presented herein, shows a remarkable (>700-fold) difference in activity between the non-irradiated and irradiated states. The photoresponsive quorum-sensing modulators can be used to control toxin production in Pseudomonas aeruginosa and have a promising outlook as next-generation research tools.

Full text of DOI:10.1016/j.chempr.2019.03.005

Article
Easily Accessible, Highly Potent,
Photocontrolled Modulators of Bacterial
Communication
Mickel J. Hansen, Jacques I.C.
Hille, Wiktor Szymanski, Arnold
J.M. Driessen, Ben L. Feringa
b.l.feringa@rug.nl
HIGHLIGHTS
Convenient, two-step synthesis of
photoswitchable quorum-sensing
modulators
>700-fold difference in activity
between the two photoisomers
Reversible photoswitching from
inhibitor to activator
Light control of toxin production
in Pseudomonas aeruginosa
By applying the photopharmacological approach, bacterial communication can be
controlled with light through the application of photoswitchable modulators.
Interestingly, one of the lead photoswitchable modulators of bacterial
communication, presented herein, shows a remarkable (>700-fold) difference in
activity between the non-irradiated and irradiated states. The photoresponsive
quorum-sensing modulators can be used to control toxin production in
Pseudomonas aeruginosa and have a promising outlook as next-generation
research tools.
Hansen et al., Chem 5, 1–9
May 9, 2019 ª 2019 Elsevier Inc.
https://doi.org/10.1016/j.chempr.2019.03.005

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
Article
Easily Accessible, Highly Potent,
Photocontrolled Modulators
of Bacterial Communication
Mickel J. Hansen,1 Jacques I.C. Hille,1 Wiktor Szymanski,1,3 Arnold J.M. Driessen,2
and Ben L. Feringa1,4,
*
SUMMARY
The Bigger Picture
Photopharmacology is an
External control of bacterial communication—quorum sensing—allows for the
regulation of a multitude of biological processes. Herein, we describe the devel-
opment of a new synthetic methodology, as well as the characterization, photo-
isomerization, and biological evaluation of a privileged series of novel photo-
switchable quorum-sensing agonists and antagonists. The presented method
allows for the rapid and convenient synthesis of previously unknown photo-
switchable agonists with up to 70% quorum-sensing induction and inhibitors
reaching up to 40% inhibition, which significantly extends the level of photocon-
trol over bacterial communication achieved before. Remarkably, for the lead
photoswitchable agonist, a >700-fold difference in activity was observed be-
tween the irradiated and non-irradiated forms, which allows for antagonism-
to-agonism switching upon exposure to light, showing levels of control unprec-
edented in photopharmacology. Finally, utilizing this system, we were able to
regulate toxin production in Pseudomonas aeruginosa with light.
emerging approach aimed at the
regulation of biological function
with light. Herein, the application
of molecular photoswitches allows
for the reversible switching
between two distinct structural
states of bioactive compounds.
Bacterial communication (quorum
sensing) is an interesting target for
photopharmacology, from the
perspective of both clinical and
basic research, because of its
implications for pathogenicity of
bacteria and complex biological
mechanism of action. By the novel
synthesis and application of
INTRODUCTION
Bacterial communication plays a vital role in the regulation of symbiotic processes
and pathogenesis of infections.1–5 The communication between bacteria is mainly
based on quorum sensing (QS), a process in which bacteria produce and excrete
QS autoinducers that are responsible for the upregulation of gene expression to
control cellular organization, virulence, and biofilm formation, among others.3,5
External control over the activity of QS autoinducers would allow the up- or down-
regulation of gene expression in bacteria, enabling remote regulation of, for
example, biofilm formation, which is becoming a major threat in the treatment of
bacterial infections, with serious implications in surgery.6–9 Moreover, complemen-
tary to the field of optogenetics, genetic engineering combined with the external
control of QS induction potentially allows the regulation of a plethora of functions
by controlling the activity of the QS operon with light.10,11
photoswitchable modulators, we
were able to reversibly control
bacterial communication with
light. Remarkably, one of our lead
compounds allows the control of
bacterial communication with very
high selectivity, switching from a
quorum-sensing inhibitor to a
quorum-sensing activator upon
irradiation with light, which was
further exemplified by the control
of quorum-sensing-regulated
toxin production in Pseudomonas
aeruginosa.
Light has proven to be an excellent stimulus for the remote control of biological sys-
tems.12,13 In this context, the emerging field of photopharmacology aims at the design
and synthesis of bioactive molecules, whose activity can be altered with light.14–17 Pho-
topharmacology relies on molecular photoswitches to control the structure of bioactive
molecules in space and time. Incorporation of photoswitches into the pharmacophore
renders the product reversibly photoresponsive. Applying the photopharmacological
approach, a variety of biological targets and tools ranging from ion channels,18–20
glutamate receptors,21,22 and G-protein-coupled receptors23 to antibiotics24–26 and
Chem 5, 1–9, May 9, 2019 ª 2019 Elsevier Inc.
1

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
anti-tumor drugs27–32 have been controlled. In the context of QS, earlier work by our
group focused on the design of photoswitchable QS autoinducers, which led to the pho-
tocontrol of QS-related gene expression and pyocyanin production.33 This proof of
concept, together with an abundance of synthetic QS ligands developed,34–36 has
paved the way for the further advancement toward more potent and selective autoin-
ducers that can be controlled with light.
Two of the major native autoinducer motifs in Pseudomonas aeruginosa, N-3-(oxo-
dodecanoyl)-L-homoserine lactone (OdDHL) and N-butyryl-L-homoserine lactone
(BHL), are depicted in Figure 1.37 These autoinducers both consist of a homoserine
lactone ‘‘head group’’ and a hydrophobic alkyl chain. Interestingly, large differences
in activity have been observed upon minor alterations of the structure, and the spec-
ificity of autoinduction is highly dependent on the bacterial strain, allowing for the
selective addressing of virulent strains over the beneficial ones.8,34 For example,
in P. aeruginosa, the 3-oxo motif seems to be inherent to the ability to induce QS,
while the BHL also shows agonistic properties albeit less pronounced.
Successful photomodulation of highly potent QS autoinducers requires the synthetic
access to 3-oxo homoserine lactones. However, the photoswitchable derivatives of
3-oxo homoserine lactone cannot be made via conventional synthetic methodology.
While the original synthesis of the native 3-oxo derivative is performed using a low-
yielding derivatization of Meldrum’s acid that poses problems with both stability
(decarboxylation) and purification when non-alkyl substrates are used,38,39 efforts
by the Blackwell group led to the development of an elegant, microwave-
assisted synthetic sequence.40 However, simple dianion formation and nucleophilic
substitution, in our hands, did not give satisfying results either; especially
the reported protection-deprotection strategy proved troublesome with our
azobenzene-based substrates, while we anticipated that elevated temperatures
with microwave irradiation potentially would pose problems with the photoswitch
scaffold. In developing a new, efficient synthetic pathway toward aryl-substituted
3-oxo homoserine lactones, we were inspired by earlier reports from the groups of
Buchwald on the cross-coupling of esters and ketones to aryl chlorides41 and
Skrydstrup on carbonylative vinylogous couplings with dioxinone,42 which provided
evidence that an unprecedented cross-coupling reaction between chlorobenzene
and dioxinone could potentially allow the facile synthesis of a protected 3-oxo pre-
cursor. Our initial investigations focused on the development and optimization of
such a cross-coupling reaction to synthesize aryl-b-keto-amides.
RESULTS AND DISCUSSION
A model reaction of chlorobenzene (1 equiv) and dioxinone (1.1 equiv) with catalytic
tBuXPhos-Pd-G1 and 3 equiv LiHMDS in toluene under ambient conditions for
1Centre for Systems Chemistry, Stratingh Institute
for Chemistry, University of Groningen,
Nijenborgh 4, Groningen 9747 AG, the
30 min yielded the desired coupling product 1 in a remarkably high yield without
the need for laborious purification (Figure 2C). To our delight, the reaction of
p-chloroazobenzene (1 equiv) with dioxinone (1 equiv) under similar conditions
also proceeded with a >95% isolated yield after 30 min reaction time without the
need for chromatographic purification. Next, the synthesized intermediate was re-
acted with homoserine lactone in the presence of a base at elevated temperatures
(110ꢀC) to yield the desired photoswitchable 3-oxo homoserine lactone AHL1.
Full conversion was obtained after 3 h with only minor impurities, as observed
from 1H-NMR spectroscopy. Purification by flash chromatography yielded the
pure product in a satisfying yield. The versatility of this two-step method to prepare
highly valuable aryl-3-oxo homoserine lactones was further demonstrated by the
Netherlands
2Molecular Microbiology, Groningen
Biomolecular Sciences and Biotechnology
Institute, Nijenborgh 7, Groningen 9747 AG, the
Netherlands
3University Medical Center Groningen,
Department of Radiology, Medical Imaging
Center, University of Groningen, Hanzeplein 1,
Groningen 9713 GZ, the Netherlands
4Lead Contact
*Correspondence: b.l.feringa@rug.nl
https://doi.org/10.1016/j.chempr.2019.03.005
2
Chem 5, 1–9, May 9, 2019

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
Figure 1. Concept of Photocontrolled Modulators of Bacterial Communication Starting from Native QS Autoinducers toward a Photoswitchable
Agonist and Antagonist Toolbox
straightforward synthesis of a library of 16 photoresponsive effectors of bacterial
communication (Figure 2D). A diverse set of both azobenzenes and different anilines
or aminolactone could be used in a versatile two-step synthetic sequence without
the need for specific reaction optimization.
The library described here employs the azobenzene motif, an exceptional, versatile
class of photoswitches with distinct photochemical properties.43,44 The structure of
azobenzene can be photochemically modulated between the thermally stable trans-
isomer and the cis-isomer. The unstable cis-isomer converts thermally back to the
trans-isomer over time or upon irradiation with another wavelength of light. Utiliza-
tion of azobenzene derivatives, in a biological context, necessitates photochemical
properties such as high photostationary states, appropriate thermal half-lives, and
fatigue resistance, i.e., the ability to photoswitch for repetitive cycles without degra-
dation. Photochemical and thermal isomerization studies were performed for all
AHLs (see Figure 3; Supplemental Information), exhibiting efficient photostationary
states (>95% trans before irradiation and between 84% and 97% cis under irradia-
tion; see Supplemental Information for details). Moreover, no significant fatigue
was observed for any of the AHLs after five cycles of irradiation and half-lives for
the cis-isomer showed to be between 28 and 100 min, which is within the suitable
time range for the biological experiments performed (vide infra; see also Figure S7).
The subsequentbiologicalevaluationfocusedontheLasnetworkofP.aeruginosa, which
can bequantifiedbythe induction ofLasQSasmeasuredbyafunctionalreadoutofbiolu-
minescence in a QS reporter strain (E.coli JM109 pSB1075).45,46 In this strain, the AHLs
potentially bind to the transcriptional activator LasR to form a stable dimer, which
can bind to the responsive promoter region of the LasQS system proceeding the
luxCDABE-lasRpromoterfusionreportergenes, resultinginenhancedbioluminescence.
Initialstudies focusedonthe potential QS-inhibiting propertiesbyutilizinga competition
experiment, in which the induction of the native OdDHL was inhibited with the different
AHLs from the herein reported library (see Figure S1).45,46 Compounds (AHL13–AHL15)
Chem 5, 1–9, May 9, 2019
3

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
A
B
C
D
Figure 2. Synthetic Methodology Developed for the Preparation of a- and b-carbonyl Compounds
(A and B) Cross-couplings previously reported by (A) Skrydstrup and co-workers42 and (B) Biscoe and Buchwald.41
(C) Novel methodology for the synthesis of aryl-b-ketoamides in this work.
(D) Synthesized library of potential agonists and antagonists. A diverse set of para-substituted AHLs was prepared for investigation of the structure-
activity relationship.
4
Chem 5, 1–9, May 9, 2019

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
Figure 3. Photochemical Evaluation of AHL5
(A) Molecular structure of AHL5.
(B) Photostationary state and trans-cis ratio after thermal adaption of AHL5: thermally adapted
(black) and 365 nm irradiated (blue). See Table S1 for all AHLs.
(C) UV-visible spectra showing the photoswitching of AHL5 with an isosbestic point at 385 nm.
(D) Fatigue determination of AHL5; no significant fatigue was observed after 15 rounds of
irradiation.
(E) Kinetic evaluation of the half-life of AHL at 30ꢀC (see Figure S7; Supplemental Information for
evaluation of the half-life under assay conditions).
All measurements were performed in DMSO at a concentration of 20 mM (or DMSO-d6 at 2 mM
for B).
showed satisfactory inhibitory activity, as expected from earlier structure-activity-rela-
tionship (SAR) studies.47,48 Also, AHL1 showed good inhibitory activity against OdDHL
with a minor difference in activity between the irradiated and non-irradiated samples.
Inspired by these results, we synthesized and tested AHL16, which unfortunately ex-
hibited similar inhibition with a minor difference in activity. Notably, the 1-oxo-azo, re-
ported before by our group,33 proved to be the most potent photoswitchable inhibitor
in our library with 57% inhibition of QS activity.
Next, we tested the agonizing properties of the synthesized AHLs. Remarkably, only
limited enhancement of the activity was observed for the 3-oxo AHL1 when
compared with the previously reported 1-oxo-azo derivative,33 whereas from previ-
ous SAR studies,8,34 a considerable enhancement was expected. However, substitu-
tion of the azobenzene core had a major effect on the agonistic properties of the
resulting photoswitchable AHLs. At the thermally stable states, both p-propyl and
p-fluoro AHLs (AHL4 and AHL9) proved to be the main agonists of QS in this library
with 15%–18% induction (compared with that of the native AHL, OdDHL; Figure 1).
However, irradiation (l = 365 nm for 5 min) of the AHLs and subsequent evaluation as
QS agonists revealed a dramatic increase in activity for AHL3–AHL7 and AHL10,
whereas the activity of AHL9 showed a notable decrease (see Figure 4). Especially
AHL4 and AHL5 stood out in this respect with 71% and 46% QS induction,
Chem 5, 1–9, May 9, 2019
5

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
Figure 4. Biological Evaluation of Photocontrolled Quorum-Sensing Autoinducers
All compounds were evaluated at 5 mM, with E. coli JM109 psB1075 as the reporter strain, after
65 min of incubation. Native autoinducer OdDHL was used as a positive control. Measurements all
represent the mean of triplicates with standard deviation. AHLs were used in their thermally
adapted form (red, trans-isomer) or were pre-irradiated for 5 min with l = 365 nm light (blue, mainly
cis-isomer) (see Supplemental Information for details).
respectively. The activity of irradiated AHL4 is closely comparable to the best known
synthetic autoinducers reported so far.8,35 From the small library reported herein, it
can be concluded that the alkyl substituent at the para-position is crucial to enhance
activity upon photoisomerization. As shown in Figure 4 (AHL1–AHL7), elongation of
the hydrophobic tail initially increases the activity until it reaches a maximum at the
C3 tail, whereas further elongation up to a C6 substituent leads to a loss of activity.
Moreover, the selectivity of the cis-isomer (over the trans-isomer) also significantly
changes with the substitution pattern. A profound 12-fold difference in activity at a
single concentration (5 mM) between the irradiated and non-irradiated form was
observed for AHL5. Subsequent investigation of the dose response of both the irra-
diated and non-irradiated AHL5 (see Figure 5A) revealed a stunning >700-fold differ-
ence in activity between the irradiated (cis, EC50 = 0.57 mM) and non-irradiated (trans,
no activity up to 400 mM; see Supplemental Information for details) forms. This
difference in activity represents an unprecedented selectivity in photopharmacol-
ogy, hitherto observed only for irreversible activation of photocaged systems,49
and additionally illustrates the sensitivity of the LasQS system. Remarkably, the irra-
diated form showed a threshold at which activation reached the maximum. After
100 mM, the activity significantly decreased without interfering with bacterial growth
(see Supplemental Information for details). All the tested compounds showed no
antibacterial activity, i.e., the AHLs did not alter the growth of the reporter strain at
relevant concentrations (see Supplemental Information for growth curves), proving
that the drop of the QS signal is not caused by compound toxicity and cell death.
To emphasize the reversibility of the induction attained with photoswitchable AHL5 and
exclude the possibility that the difference in potency between the two forms of AHL5
stems from photodegradation to a more potent compound, we sequentially activated
and deactivated this compound with different wavelengths of light. As can be observed
from Figure 5B, at least two cycles of activation and deactivation with 365 nm and WL are
feasible without the observation of significant fatigue or degradation. Moreover, the lack
6
Chem 5, 1–9, May 9, 2019

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
Figure 5. Dose-Response Profile and Fatigue Resistance of AHL5
(A) Relative luminescence obtained at different concentrations of AHL5. A dramatic difference in
agonizing activity was observed between irradiated and non-irradiated samples.
(B) Repetitive switching cycles without observable fatigue. l1, 365 nm for 5 min; l2, white light for
1 min; [AHL5], 5 mM in Luria Bertani (LB) broth with <1% DMSO.
(C) Antagonist to agonist switching of AHL5 (60 mM): 0% relative QS activity was induced by the EC50
concentration (0.6 nM) of OdDHL, and À100% activation (100% inhibition) is based on a blank with
the appropriate DMSO concentration (see Supplemental Information for details; Figure S8).
(D) Pyocyanin production in Pseudomonas aeruginosa (PA14 DlasI) upon exposure to a negative
control (2% DMSO), positive control (20 mM ODdHL), and AHL5 (2 3 50 mM) without (red) and after
(blue) irradiation (see Supplemental Information for details).
of agonizing activity, even at increasing concentrations of our non-irradiated AHL5,
raised the question whether the trans-AHL5 would potentially possess antagonizing
properties. To evaluate such behavior, we induced QS activation by EC50 concentrations
of the native autoinducer (OdDHL). The induction of limited QS activity allows both QS
activation and inhibition to be measured. Interestingly, at a concentration of 60 mM,
AHL5 could be reversibly switched from a QS inhibitor (30% inhibition) to a QS activator
(upto60%activation)uponirradiationwithlight.Thisshowcasesoneofthefirstexamples
of the photopharmacological approach with opposing activities (inhibitor versus acti-
vator) of the different isomers.23 Next, we applied AHL5 to P. aeruginosa (PA14 DlasI)
to control toxin production (pyocyanin) with light. Pyocyanin production is under direct
QS control, making it an interesting target to confirm the applicability of our approach
in vitro. Utilizing AHL5 in the non-irradiated and irradiated form resulted in a significant
difference in pyocyanin levels (7% and 48%, respectively), confirming the ability to con-
trol QS-regulated phenotypes with light using the photoswitchable modulators pre-
sented here.
In conclusion, we have developed a synthetic methodology to gain access to a
library of photoswitchable 3-oxo-derived QS agonists and antagonists via a novel
Pd-catalyzed cross-coupling reaction. Up to 71% QS induction was obtained,
whereas the best inhibitor showed almost 40% OdDHL inhibition. Moreover, our
Chem 5, 1–9, May 9, 2019
7

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
lead compound, AHL5, showed privileged properties for further development in
photopharmacology because of the excellent difference in activity between the
inactive (non-irradiated) and activated (irradiated) states. Strikingly, utilizing revers-
ible photoswitching, a >700-fold difference in activity between the irradiated and
non-irradiated forms has been achieved, which could be translated to a significant
phenotypic effect, i.e., toxin production in P. aeruginosa. Furthermore, the
possibility to switch from a QS inhibitor to a QS activator by using light opens up
new possibilities in photopharmacology and QS research. This excellent photophar-
macological behavior paves the way for future application of these novel photo-
switchable QS agonists, and distinct AHLs from the here-reported series are highly
promising as next-generation light-controlled research tools.
SUPPLEMENTAL INFORMATION
Supplemental Information can be found online at https://doi.org/10.1016/j.chempr.
2019.03.005.
ACKNOWLEDGMENTS
This work was financially supported by the Netherlands Organization for Scientific
Research (NWO-CW, TOP grant to B.L.F. and NWO VIDI grant 723.014.001 to
W.S.), the Royal Netherlands Academy of Arts and Sciences (KNAW), the Ministry
of Education, Culture and Science (Gravitation programme 024.001.035), and the
European Research Council (Advanced Investigator grant 694345 to B.L.F.).
AUTHOR CONTRIBUTIONS
Conceptualization, M.J.H., W.S., A.J.M.D., and B.L.F.; Methodology, M.J.H. and
J.I.C.H.; Investigation, M.J.H. and J.I.C.H.; Writing – Original Draft, M.J.H.; Writing –
Review & Editing, M.J.H., W.S., A.J.M.D., and B.L.F.; Resources, W.S., A.J.M.D., and
B.L.F.; Supervision, W.S., A.J.M.D., and B.L.F.
DECLARATION OF INTERESTS
The authors declare no competing interests.
Received: October 29, 2018
Revised: December 12, 2018
Accepted: March 12, 2019
Published: April 15, 2019
REFERENCES AND NOTES
1. Greenberg, E.P. (2003). Bacterial
communication: tiny teamwork. Nature 424,
134.
compound development to biological
discovery. FEMS Microbiol. Rev. 40, 774–794.
susceptibility, phenotypic response, and next-
generation ligand design. J. Am. Chem. Soc.
137, 14626–14639.
6. Stevens, A.M., Queneau, Y., Soule` re, L., von
Bodman, S., and Doutheau, A. (2011).
Mechanisms and synthetic modulators of AHL-
dependent gene regulation. Chem. Rev. 111,
4–27.
9. Wysoczynski-Horita, C.L., Boursier, M.E., Hill,
R., Hansen, K., Blackwell, H.E., and Churchill,
M.E.A. (2018). Mechanism of agonism and
antagonism of the Pseudomonas aeruginosa
quorum sensing regulator QscR with non-
native ligands. Mol. Microbiol. 108, 240–257.
2. Camilli, A., and Bassler, B.L. (2006). Bacterial
small-molecule signaling pathways. Science
311, 1113–1116.
3. Rasko, D.A., and Sperandio, V. (2010). Anti-
virulence strategies to combat bacteria-
mediated disease. Nat. Rev. Drug Discov. 9,
117–128.
7. Fuqua, C., Parsek, M.R., and Greenberg, E.P.
(2001). Regulation of gene expression by cell-
to-cell communication: acyl-homoserine
lactone quorum sensing. Annu. Rev. Genet. 35,
439–468.
10. Young, D.D., and Deiters, A. (2007).
Photochemical activation of protein expression
in bacterial cells. Angew. Chem. Int. Ed. 46,
4290–4292.
4. Fuqua, C., and Greenberg, E.P. (2002).
Listening in on bacteria: acyl-homoserine
lactone signalling. Nat. Rev. Mol. Cell Biol. 3,
685–695.
8. Moore, J.D., Rossi, F.M., Welsh, M.A., Nyffeler,
K.E., and Blackwell, H.E. (2015). A comparative
analysis of synthetic quorum sensing
modulators in Pseudomonas aeruginosa: new
insights into mechanism, active efflux
11. Kramer, R.H., Mourot, A., and Adesnik, H.
(2013). Optogenetic pharmacology for control
of native neuronal signaling proteins. Nat.
Neurosci. 16, 816–823.
5. Welsh, M.A., and Blackwell, H.E. (2016).
Chemical probes of quorum sensing: from
8
Chem 5, 1–9, May 9, 2019

Please cite this article in press as: Hansen et al., Easily Accessible, Highly Potent, Photocontrolled Modulators of Bacterial Communication, Chem
(2019), https://doi.org/10.1016/j.chempr.2019.03.005
ꢀ
12. Szymanski, W., Beierle, J.M., Kistemaker,
antimicrobial chemotherapy using
photoswitchable amidohydrolase inhibitors.
ACS Infect. Dis. 3, 152–161.
potential for interspecies bacterial signaling.
ACS Chem. Biol. 12, 2457–2464.
H.A.V., Velema, W.A., and Feringa, B.L. (2013).
Reversible photocontrol of biological systems
by the incorporation of molecular
38. McInnis, C.E., and Blackwell, H.E. (2011).
Design, synthesis, and biological evaluation of
abiotic, non-lactone modulators of LuxR-type
quorum sensing. Bioorg. Med. Chem. 19,
4812–4819.
27. Hansen, M.J., Velema, W.A., de Bruin, G.,
Overkleeft, H.S., Szymanski, W., and Feringa,
B.L. (2014). Proteasome inhibitors with
photocontrolled activity. Chembiochem 15,
2053–2057.
photoswitches. Chem. Rev. 113, 6114–6178.
13. Ankenbruck, N., Courtney, T., Naro, Y., and
Deiters, A. (2018). Optochemical control of
biological processes in cells and animals.
Angew. Chem. Int. Ed. 57, 2768–2798.
39. Miller, L.C., O’Loughlin, C.T., Zhang, Z.,
Siryaporn, A., Silpe, J.E., Bassler, B.L., and
Semmelhack, M.F. (2015). Development of
potent inhibitors of pyocyanin production in
Pseudomonas aeruginosa. J. Med. Chem. 58,
1298–1306.
28. Borowiak, M., Nahaboo, W., Reynders, M.,
Nekolla, K., Jalinot, P., Hasserodt, J., Rehberg,
M., Delattre, M., Zahler, S., Vollmar, A., et al.
(2015). Photoswitchable inhibitors of
14. Velema, W.A., Szymanski, W., and Feringa, B.L.
(2014). Photopharmacology: beyond proof of
principle. J. Am. Chem. Soc. 136, 2178–2191.
microtubule dynamics optically control mitosis
and cell death. Cell 162, 403–411.
15. Broichhagen, J., Frank, J.A., and Trauner, D.
(2015). A roadmap to success in
photopharmacology. Acc. Chem. Res. 48,
1947–1960.
40. Geske, G.D., Wezeman, R.J., Siegel, A.P., and
Blackwell, H.E. (2005). Small molecule
inhibitors of bacterial quorum sensing and
biofilm formation. J. Am. Chem. Soc. 127,
12762–12763.
29. Simeth, N.A., Altmann, L.M., Wossner, N.,
¨
Bauer, E., Jung, M., and Konig, B. (2018).
¨
Photochromic indolyl fulgimides as chromo-
pharmacophores targeting sirtuins. J. Org.
Chem. 83, 7919–7927.
16. Lerch, M.M., Hansen, M.J., van Dam, G.M.,
Szymanski, W., and Feringa, B.L. (2016).
Emerging targets in photopharmacology.
Angew. Chem. Int. Ed. 55, 10978–10999.
41. Biscoe, M.R., and Buchwald, S.L. (2009).
Selective monoarylation of acetate esters and
aryl methyl ketones using aryl chlorides. Org.
Lett. 11, 1773–1775.
30. Babii, O., Afonin, S., Garmanchuk, L.V.,
Nikulina, V.V., Nikolaienka, T.V., Storozhuk,
O.V., Shelest, D.V., Dasyukevich, O.I.,
Ostapchenko, L.I., Iurchenko, V., et al. (2016).
Direct photocontrol of peptidomimetics: an
alternative to oxygen-dependent
17. Hull, K., Morstein, J., and Trauner, D. (2018).
¨
In vivo photopharmacology. Chem. Rev. 118,
10710–10747.
42. Makarov, I.S., Kuwahara, T., Jusseau, X., Ryu, I.,
Lindhardt, A.T., and Skrydstrup, T. (2015).
18. Zemelman, B.V., Nesnas, N., Lee, G.A., and
Miesenbock, G. (2003). Photochemical gating
of heterologous ion channels: remote control
over genetically designated populations of
neurons. Proc. Natl. Acad. Sci. USA 100, 1352–
1357.
Palladium-catalyzed carbonylative couplings of
vinylogous enolates: application to statin
structures. J. Am. Chem. Soc. 137, 14043–14046.
photodynamic cancer therapy. Angew. Chem.
Int. Ed. 55, 5493–5496.
31. Rastogi, S.K., Zhao, Z., Barrett, S.L., Shelton,
S.D., Zafferani, M., Anderson, H.E., Blumenthal,
M.O., Jones, L.R., Wang, L., Li, X., et al. (2018).
Photoresponsive azo-combretastatin A-4
analogues. Eur. J. Med. Chem. 143, 1–7.
43. Beharry, A.A., and Woolley, G.A. (2011).
Azobenzene photoswitches for biomolecules.
Chem. Soc. Rev. 40, 4422–4437.
19. Koc¸er, A., Walko, M., Meijberg, W., and
Feringa, B.L. (2005). A light-actuated nanovalve
derived from a channel protein. Science 309,
755–758.
44. B.L. Feringa, and W.R. Browne, eds. (2011).
Molecular Switches (Wiley, VCH Verlag GmbH
& Co. KGaA).
32. Matera, C., Gomila, A.M.J., Camarero, N.,
Libergoli, M., Soler, C., and Gorostiza, P. (2018).
Photoswitchable antimetabolite for targeted
photoactivated chemotherapy. J. Am. Chem.
Soc. 140, 15764–15773.
20. Frank, J.A., Moroni, M., Moshourab, R.,
Sumser, M., Lewin, G.R., and Trauner, D. (2015).
Photoswitchable fatty acids enable optical
control of TRPV1. Nat. Commun. 6, 7118.
45. Holden, M.T.G., Ram Chhabra, S., De Nys, R.,
Stead, P., Bainton, N.J., Hill, P.J., Manefield,
M., Kumar, N., Labatte, M., England, D., et al.
(1999). Quorum-sensing cross talk: isolation
and chemical characterization of cyclic
dipeptides from Pseudomonas aeruginosa and
other Gram-negative bacteria. Mol. Microbiol.
33, 1254–1266.
33. Van der Berg, J.P., Velema, W.A., Szymanski,
W., Driessen, A.J.M., and Feringa, B.L. (2015).
Controlling the activity of quorum sensing
autoinducers with light. Chem. Sci. 6, 3593–
3598.
21. Volgraf, M., Gorostiza, P., Numano, R., Kramer,
R.H., Isacoff, E.Y., and Trauner, D. (2006).
Allosteric control of an ionotropic glutamate
receptor with an optical switch. Nat. Chem.
Biol. 2, 47–52.
46. Winson, M.K., Swift, S., Fish, L., Throup, J.P.,
Jorggensen, F., Chhabra, S.R., Bycroft, B.W.,
Williams, P., and Stewart, G.S. (1998).
34. Geske, G.D., O’Neill, J.C., Miller, D.M.,
Wezeman, R.J., Mattmann, M.E., Lin, Q., and
Blackwell, H.E. (2008). Comparative analyses of
N-acylated homoserine lactones reveal unique
structural features that dictate their ability to
activate or inhibit quorum sensing.
22. Reiner, A., and Isacoff, E.Y. (2014). Tethered
ligands reveal glutamate receptor
Construction and analysis of luxCDABE -based
plasmid sensors for investigating N-acyl
homoserine lactone-mediated quorum
desensitization depends on subunit
occupancy. Nat. Chem. Biol. 10, 273–280.
sensing. FEMS Microbiol. Lett. 163, 185–192.
Chembiochem 9, 389–400.
23. Go´ mez-Santacana, X., de Munnik, S.M.,
Vijayachandran, P., Da Costa Pereira, D.,
Bebelman, J.P.M., de Esch, I.J.P., Vischer, H.F.,
Wijtmans, M., and Leurs, R. (2018).
47. Morkunas, B., Galloway, W.R.J.D., Wright, M.,
Ibbeson, B.M., Hodgkinson, J.T., O’Connell,
K.M.G., Bartolucci, N., Della Valle, M., Welch,
M., and Spring, D.R. (2012). Inhibition of the
production of the Pseudomonas aeruginosa
virulence factor pyocyanin in wild-type cells by
quorum sensing autoinducer-mimics. Org.
Biomol. Chem. 10, 8452–8464.
35. Boursier, M.E., Manson, D.E., Combs, J.B., and
Blackwell, H.E. (2018). A comparative study of
non-native N-acyl l-homoserine lactone
Photoswitching the efficacy of a small-molecule
ligand for a peptidergic GPCR: from
antagonism to agonism. Angew. Chem. Int. Ed.
57, 11608–11612.
analogs in two Pseudomonas aeruginosa
quorum sensing receptors that share a
common native ligand yet inversely regulate
virulence. Bioorg. Med. Chem. 26, 5336–5342.
24. Velema, W.A., van der Berg, J.P., Hansen, M.J.,
Szymanski, W., Driessen, A.J.M., and Feringa,
B.L. (2013). Optical control of antibacterial
activity. Nat. Chem. 5, 924–928.
36. Hodgkinson, J.T., Galloway, W.R.J.D., Wright,
M., Mati, I.K., Nicholson, R.L., Welch, M., and
Spring, D.R. (2012). Design, synthesis and
biological evaluation of non-natural
modulators of quorum sensing in
48. Mattmann, M.E., Geske, G.D., Worzalla, G.A.,
Chandler, J.R., Sappington, K.J., Greenberg,
E.P., and Blackwell, H.E. (2008). Synthetic
ligands that activate and inhibit a quorum-
sensing regulator in Pseudomonas aeruginosa.
Bioorg. Med. Chem. Lett. 18, 3072–3075.
25. Wegener, M., Hansen, M.J., Driessen, A.J.M.,
Szymanski, W., and Feringa, B.L. (2017).
Photocontrol of antibacterial activity: shifting
from UV to red light activation. J. Am. Chem.
Soc. 139, 17979–17986.
Pseudomonas aeruginosa. Org. Biomol. Chem.
10, 6032–6044.
37. Gerdt, J.P., Wittenwyler, D.M., Combs, J.B.,
Boursier, M.E., Brummond, J.W., Xu, H., and
Blackwell, H.E. (2017). Chemical interrogation
of LuxR-type quorum sensing receptors reveals
new insights into receptor selectivity and the
49. Knoll, J.D., and Turro, C. (2015). Control and
utilization of ruthenium and rhodium metal
complex excited states for photoactivated
cancer therapy. Coord. Chem. Rev. 282–283,
110–126.
¨
26. Weston, C.E., Kramer, A., Colin, F., Yildiz, O.,
¨
Baud, M.G.J., Meyer-Almes, F.J., and Fuchter,
M.J. (2017). Toward photopharmacological
Chem 5, 1–9, May 9, 2019
9