. 2021 Apr 13;12:659464. doi: 10.3389/fmicb.2021.659464

Table 2.

Ion motive force (IMF) and ion related conditions shown to be necessary, ✓, or not, ✗, for stator assembly.

Condition	Necessary for assembly?	Ion	Species	References
PMF	(✓)	H⁺	E. coli	Fung and Berg, 1995
	✓	H⁺	E. coli	Tipping J. M. et al., 2013
	✗	H⁺	E. coli	Suzuki et al., 2019
	✗	H⁺	S. enterica	Morimoto et al., 2010
	✗	H⁺	S. enterica	Suzuki et al., 2019
SMF	✓	Na⁺	V. alginolyticus	Fukuoka et al., 2009
ΔpH	✗	H⁺	E. coli	Fung and Berg, 1995
	✗	H⁺	E. coli	Suzuki et al., 2019
	✗	H⁺	S. enterica	Morimoto et al., 2010
	✗	H⁺	S. enterica	Suzuki et al., 2019
pH_ext	✓	H⁺	E. coli	Suzuki et al., 2019
	✓	H⁺	S. enterica	Suzuki et al., 2019
[Na⁺]_ext or ΔpNa	(✓)	Na⁺	E. coli	Sowa et al., 2005
	(✓)	Na⁺	E. coli	Sowa et al., 2014
	✓	Na⁺	V. alginolyticus	Fukuoka et al., 2009
	✓	Na⁺	B. subtilis	Terahara et al., 2017
	✗	Na⁺	S. oneidensis	Paulick et al., 2015
	✗	H⁺	S. oneidensis	Paulick et al., 2009
	✗	H⁺	B. subtilis	Terahara et al., 2017
H⁺ conduction	(✗)	H⁺	E. coli	Zhou et al., 1998
	(✗)	H⁺	E. coli	Kojima and Blair, 2001
	✗	H⁺	E. coli	Suzuki et al., 2019
	✗	H⁺	S. enterica	Morimoto et al., 2010
	✗	H⁺	S. enterica	Suzuki et al., 2019
Na⁺ conduction	✓	Na⁺	V. alginolyticus	Fukuoka et al., 2009
	(✓)	Na⁺	B. subtilis	Terahara et al., 2017

Marks in parentheses denote indirect evidence for assembly, either via measurements of motor/swimming speed (Fung and Berg, 1995; Zhou et al., 1998; Kojima and Blair, 2001; Sowa et al., 2005, 2014), wherein it cannot be ruled out that the stators are assembled but somehow inactive, or via a structural switch of the stator complex that suggests peptidoglycan (PG) binding (Terahara et al., 2017).