Table 1.

Physiological role of TonB-dependent receptors (TBDTs).

Substrates	TBDTs	Genomes	Evidence	References
Iron-siderophore complex	FauA	Bordetella pertussis	Ex	[41]
	FecA	Escherichia coli	Ex	[42]
	FepA	Escherichia coli	Ex	[43]
	FhuA	Escherichia coli	Ex	[44]
	FptA	Pseudomonas aeruginosa	Ex	[45]
	FpvA	Pseudomonas aeruginosa	Ex	[46]
	FrpB	Neisseria meningitidis	Ex	[47]
	FyuA	Yersenia pestis	Ex	[48]
	HemR	Yersenia enterocolitica	Ex	[49]
	TbpA	Neisseria meningitidis	Ex	[47]
Cobalamins	BtuB	Escherichia coli	Ex	[50]
	BPSL0976	Burkholderia pseudomallei	Pr	[51]
	PA1271	Pseudomonas aeruginosa	Pr	[51]
	PA2911	Pseudomonas aeruginosa	Pr	[51]
	RS02718	Ralstonia solanacearum	Pr	[51]
	RSP_2402	Rhodbacter sphaeroides	Pr	[51]
Sucrose	SuxA	Xanthomonas campestris	Ex	[8]
	Sfri_3988	Shewanella frigidimarina	Pr	[8]
Maltose	MalA	Caulobacter vibrioides	Ex	[52]
Chitin	XCC2469	Xanthomonas campestris	Pr	[53]
	XCC2944	Xanthomonas campestris	Pr	[53]
	CPS_1021	Colwellia psychrerythraea	Pr	[53]
	Sden_2708	Shewanella denitrificans	Pr	[53]
Xylan	XCC4120	Xanthomonas campestris	Pr	[8]
Copper	NosA	Pseudomonas stutzeri	Pr	[54,55]
	OprC	Pseudomonas aeruginosa	Pr	[54,55]
	NosA	Pseudomonas putida	Ex	[54,55]
	OprC	Pseudomonas putida	Ex	[54,55]
Nickel	FrpB4	Helicobacter pylori	Ex	[13]
	Daro_3944	Dechloromonas aromatica	Pr	[56]
	BLL6948	Bradyrhizobium diazoefficiens	Pr	[56]
	IL54_0463	Sphingobium sp. ba1	Tr	[16]
	IL54_3057	Sphingobium sp. ba1	Tr	[16]
Thiamin	BF0615	Bacteroides fragilis	Pr	[57]
	CPS_0067	Colwellia psychrerythraea	Pr	[57]
	Sputw3181_2365	Shewanella	Pr	[57]
	GOX1347	Gluconobacter oxydans	Pr	[57]
Cobalt	Daro_1684	Dechloromonas aromatica	Pr	[56]
Pectin	XCC0120	Xanthomonas campestris	Pr	[8]
Colicin	CirA	Escherichia coli	Ex	[58]
Heme	HasR	Serratia marcescens	Ex	[49]
	ShuA	Shigella dysenteriae	Ex	[59]
Sulfanilic acid	BES08_08830	Novosphingobium resinovorans SA1	Tr	[36]
	BES08_18055	Novosphingobium resinovorans SA1	Tr	[36]
	BES08_18430	Novosphingobium resinovorans SA1	Tr	[36]
	BES08_18580	Novosphingobium resinovorans SA1	Tr	[36]
	BES08_22625	Novosphingobium resinovorans SA1	Tr	[36]
	BES08_23675	Novosphingobium resinovorans SA1	Tr	[36]
	BES08_26825	Novosphingobium resinovorans SA1	Tr	[36]
Various substrates under nutrient limitation	Sala_0027	Sphingopyxis alaskensis RB2256	Tr	[14]
	Sala_0914	Sphingopyxis alaskensis RB2256	Tr	[14]
	Sala_1228	Sphingopyxis alaskensis RB2256	Tr	[14]
	Sala_1913	Sphingopyxis alaskensis RB2256	Tr	[38]
	Sala_3029	Sphingopyxis alaskensis RB2256	Tr	[14]
	Sala_3108	Sphingopyxis alaskensis RB2256	Tr	[14]
	Saro_0168	Novosphingobium aromaticivorans DSM 12444	Tr	[14]
	Saro_1603	Novosphingobium aromaticivorans DSM 12444	Tr	[14]
	SKA58_00625	Sphingomonas sp. SKA58	Tr	[14]
	SKA58_14617	Sphingomonas sp. SKA58	Tr	[14]
	SKA58_18137	Sphingomonas sp. SKA58	Tr	[14]
Dibenzo-p-dioxin	Swit_0277	Sphingomonas wittichii RW1	Tr	[33]
	Swit_1066	Sphingomonas wittichii RW1	Tr	[33]
	Swit_3263	Sphingomonas wittichii RW1	Tr	[33]
	Swit_4088	Sphingomonas wittichii RW1	Tr	[33]
	Swit_4197	Sphingomonas wittichii RW1	Tr	[33]
Dibenzofuran	Swit_0687	Sphingomonas wittichii RW1	Tr	[33]
	Swit_2477	Sphingomonas wittichii RW1	Tr	[33]
	Swit_3189	Sphingomonas wittichii RW1	Tr	[33]
	Swit_3918	Sphingomonas wittichii RW1	Tr	[33]
	Swit_4025	Sphingomonas wittichii RW1	Tr	[33]
	Swit_4696	Sphingomonas wittichii RW1	Tr	[33]
	Swit_4781	Sphingomonas wittichii RW1	Tr	[33]

Ex: experimentally validated, Pr: predicted, Tr: transcriptome and proteome analysis.