Table 3.

Modules available for osmolytes, cell-cell signals, and other common environmental parameters.

Analyte sensed		Name	Mechanism	Mode of prior use	Application	References
Osmolytes	Osmotic stress	proU promoter	TR	P. putida, P agglomerans	Soil	Herron et al., 2010
	Trimethylamine N-oxide	TorTSR	TCS	E. coli	N/A	Schmidl et al., 2019
	Ectoine	AraC-ect	TR	E. coli	N/A	Chen et al., 2015
	Glutamate	DegS-EnvZ	TCS	E. coli	N/A	Ravikumar et al., 2018
	Glycine betaine	CFP, GBP, & YFP	PS	E. coli	N/A	Ahmad et al., 2016
Cell-cell signals	C6 AHL	LuxR	TR	E. coli	Soil	Cheng et al., 2018
		ScbR	TR	Cell-free	N/A	Yang et al., 2009
	C12 AHL	LasR	TR	E. coli	Soil	Cheng et al., 2018
		LasR	TR	Cell-free	Sputum	Wen et al., 2017
	Quercetin	QdoR	TR	E. coli	DOC	Del Valle et al., 2020
	Naringenin	FdeR	TR	E. coli	DOC	Del Valle et al., 2020
		TtgR	TR	Cell-free	N/A	Jung et al., 2020
	Luteolin	FdeR	TR	E. coli	DOC	Del Valle et al., 2020
		NodD1-FdeR	TR	E. coli	N/A	De Paepe et al., 2019
	Kaempferol	QdoR	TR	E. coli	N/A	Siedler et al., 2014
	γ-butyrolactones	SbcR	TR	Cell-free	N/A	Yang et al., 2009
	Salicylic acid	NahR	TR	E. coli	N/A	Meyer et al., 2019
	Ethylene	SynEtr1	TCS	Synechocystis sp.	N/A	Lacey and Binder, 2016
	AIP	AgrAC	TCS	S. aureus	N/A	Sturme et al., 2002
	GBAP	FscAC	TCS	E. faecalis	N/A	Sturme et al., 2002
	Phr	Rap	TR	B. subtilis	N/A	Bareia et al., 2018
	ComX	ComAP	TCS	B. subtilis	N/A	Bareia et al., 2018
Light	UV-violet	UirSR	TCS	E. coli	N/A	Ramakrishnan and Tabor, 2016
	Blue	YF1-FixJ	TCS	E. coli	N/A	Möglich et al., 2009
	Blue	Vvd	PS	E. coli	N/A	Sheets et al., 2020
	Green	CsaSR	TCS	E. coli	N/A	Tabor et al., 2011
	Red	Cph8-EnvZ	TCS	E. coli	N/A	Levskaya et al., 2005
pH	5–7	RstA	TCS	E. coli	N/A	Hoynes-O'Connor et al., 2017
	5.5–7	VirA-ChvE	TCS	A. tumefaciens	N/A	Gao and Lynn, 2005
	6–8	SO_4387; SO_4388	TCS	E. coli	N/A	Schmidl et al., 2019
Temperature	27–37°C	CspA	TR	E. coli	N/A	Hoynes-O'Connor et al., 2017
	32–46°C	TlpA & Tcl	TR	E. coli	Mouse tissue	Piraner et al., 2017
	25–40°C	TEV & CI	TR	E. coli	N/A	Zheng et al., 2019
	29–37°C	RNAs	RS	Cell-free	N/A	Sen et al., 2017

Modules listed include both natural and engineered sensors which use a single transcriptional regulator (TR), two-component system (TCS), a protein switch (PS), or riboswitch (RS) to convert environmental information into biochemical information. This list excludes sensors which require electrochemical components. For each sensor, the table notes whether the mode of prior use has been within a cell, cell-free system, or isolated biomolecule. Additionally, it notes whether there has been a complex sample application in soil, dissolved organic carbon (DOC), sputum, or animals. Most sensors have not yet been applied (N/A) in a complex environmental setting.