Siderophore-mediated transport of molybdenum inAzospirillum lipoferum strain D-2

A catechol-type compound was secreted byAzospirillum lipoferum D-2 in the growth medium when the cells became molybdenum-limited. The compound was identified as 3,5-dihydroxybenzoic acid. Production of 3.5-DHBA occurred under both molybdenum-limited as well as supplemented conditions. Presence of iron resulted in decreased production of 3,5-DHBA in the former case, whereas in the latter case it completely suppressed production of this compound. Spectral changes revealed coordination of molybdenum with 3,5-DHBA. Presence of 3,5-DHBA enhanced uptake of molybdenum. Appearance of a new 78-Kdal protein and hyperproduction of a 88-Kdal protein in the membrane fraction were the consequence of molybdenum limitation.