The iron transport in the extremely halophilic Euryarchaeon Halobacterium salinarum JW5 was investigated. Experiments to detect endogenous siderophores from H. salinarum failed, but it was able to utilize exogenous siderophores. Measurement of the uptake of 55Fe and [14C]citrate gave evidence only for the accumulation of iron. Two additional membrane proteins could be detected in iron-starved cells, one in iron-repleted membranes and one that is up-regulated there. Respiratory rates of iron-starved membranes after the addition of succinate and NADH differed considerably from iron-repleted ones. Furthermore, both types of membrane exhibited different degrees of inhibition by cyanide.