Table 2.

Acquisition and efflux mechanisms and regulation of these systems in Helicobacter. List of acquisition systems and the corresponding regulatory mechanisms if known for each metal in Helicobacter. The asterisk denotes transport systems or regulatory mechanisms that have been experimentally tested in vitro and superscript A denotes systems investigated in vivo, while those with no superscript have been bioinformatically predicted or have not been experimentally examined

Metal	Intracellular condition	Transport systems (Helicobacter)	References	Regulation (Helicobacter)	References
Iron	High			*AFur	84, 85, 86
				Pfr	83
	Low	*AFeoB—ferrous iron	80	*AFur	84, 85, 86
		FecAB—ferric dicitrate	81
		FrpB—FeEnt	82
Zinc	High	CadA—effluxCzcB—efflux*ACznABC—efflux	118 118 117	*Zinc conc.	25, 114
	Low			*Fur	83
Copper	High	*CopAP—efflux*CrdAB—efflux*CzcAB—efflux	118 118	*CopP*CrdRS*Fur	144 143 83
	Low
Nickel	High	*Hpn—sequestration*HspA—sequestration*ACznABC—efflux	174 174 117	*ANikRNickel conc.	175, 176 173
	Low	*ANiuBDE	183
Cadmium	High	*CadA—ATPaseCznABC—efflux*Hpn—sequestration*HspA—sequestration	196, 197 117 174 174	*Cadmium conc.	196, 117, 174
	Low
Cobalt, magnesium, and manganese	High	*CadA	196	*PfrCobalt conc.	218 196
	Low	*FecDE*CeuE*NiuBDE*NixA*CorA	182 182 183 213 217
Bismuth, molybdenum, and tungsten	High			*Bismuth conc.	229
	Low	ModD	230