Table 2. Strains used in this study.

Background			Plasmids
Strain	Source	Relevant genotype	Plasmid 1	Plasmid 2
VS115	V. Sourjik	$\mathrm{\Delta }$YZ $\mathrm{\Delta }$FliC	pSJAB106	pZR1
VS104	Sourjik and Berg, 2002a	$\mathrm{\Delta }$CheYZ	pSJAB12	pBAD33
TSS58	this work	$\mathrm{\Delta }$RBYZ $\mathrm{\Delta }$FliC	pSJAB106	pZR1
VS149	Sourjik and Berg, 2004	$\mathrm{\Delta }$RBYZ	pVS12	pVS33
VS124	Clausznitzer et al., 2010	$\mathrm{\Delta }$CheBYZ	pSJAB12	pVS112
VS124		$\mathrm{\Delta }$CheBYZ	pSJAB12	pVS97
VS124		$\mathrm{\Delta }$CheBYZ	pSJAB12	pVS91
UU2567	Kitanovic et al., 2015	$\mathrm{\Delta }$CheRBYZ,$\mathrm{\Delta }$MCP†	pSJAB106	pPA114 Tsr
TSS1964	this work	$\mathrm{\Delta }$CheRBYZ,$\mathrm{\Delta }$MCP FliC*	pSJAB106	pPA114 Tsr
UU2614	J.S. Parkinson	CheB $\mathrm{\Delta }$(4-345)	pTrc99a	pVS91,97,112

All strains are descendants of E. coli K-12 HCB33 (RP437). In all FRET experiments, strains carry two plasmids and therefore confer resistance to chloramphenicol and ampicillin.

^†all five chemoreceptor genes tar tsr tap trg aer deleted.

*expresses sticky FliC filament (Scharf et al., 1998).