Table 1. Strains and culturing conditions.

Species	Strain	TON	TDC	Growth medium	Motility medium
Escherichia coli	AW405*	30 °C	33.5 °C	TB	0.18% MC/MotM
Salmonella typhimurium	LT2†	30 °C	33.5 °C	TB	0.18% MC/MotM
Bacillus subtilis	OI1085‡	30 °C	33.5 °C	BsMM	BsMM
Pseudomonas putida	KT2440§	30 °C	33.5 °C	TB	0.18% MC/MotM
Vibrio alginolyticus	YM4‡	RT	RT	MBc	TMN||
Pseudoalteromonas haloplanktis	ATCC 700530‡	RT	RT	MBc	MBc

BsMM, B. subtilis minimal medium; MBc, Marine Broth 2216 (Difco), clarified by centrifugation at 4,500g for 10 min; MC, (hydroxypropyl)methyl cellulose (H7509, Sigma Aldrich); MotM, E. coli motility medium; RT, room temperature; TB, tryptone broth; TMN, TMN motility medium; T_ON/T_DC, temperature of overnight/day culture, respectively.

^*Strain provided by Howard Berg (Harvard University).

^†Strain provided by Kelly Hughes (The University of Utah).

^‡Strain provided by Roman Stocker (MIT).

^§Strain provided by Carsten Beta (The University of Potsdam).

^||Some samples contained 0.002% Tween 20 to limit adhesion of bacteria to the sample chamber surfaces.

Media compositions are provided in Table 2.