THE NUTRITIONAL SELECTIVITY OF A SIDEROPHORE-CATABOLIZING BACTERIUM

The ability of a sideroPhore-catabolizing bacterium to assimilate ferr ic ion was examined. While the bacterium utilizes the siderophore defe rrioxamine B (DFB) as a carbon source, it was incapable of using the f erric ion analogue (ferrioxamine B) as an iron source. It did, however , assimilate the ferric ion of the chelator ferric nitrilotriacetic ac id and of the siderophore ferrirhodotorulic acid (ferriRA). Neither fe rriRA nor its deferrated analog (RA), however, were capable of functio ning as carbon sources for the bacterium. The microbe thus employs a ' nutritional selectivity' with respect to these two siderophores. That is, it does not use the siderophore it employs as a carbon source (DFB ) as an iron source nor does the siderophore utilized as an iron sourc e, i.e. ferriRA, nor its deferrated analog (RA), serve as carbon sourc es for the organism.