Influence of iron on growth and extracellular products of Acinetobacter baumannii

Iron is an important nutrient required by bacteria for optimal growth. Acqu isition of iron from the host where iron is restricted is an important medi ator of bacterial pathogenesis. In iron deplete chemically defined medium ( CDM-Fe) growth of Acinetobacter baumannii was restricted as compared to iro n replete medium (CDM+Fe). Bacteria developed four high molecular weight ou ter membrane proteins (OMPs) of 88, 84, 80 and 77 kDa in CDM-Fe medium whic h were absent in CDM+Fe medium, and are known iron regulated outer membrane proteins (IROMPs). A. baumannii secreted siderophores extracellularly into the medium which act as iron chelators which had been demonstrated in the supernatants of CDM-Fe media. The siderophore was of catechol type. This sh ows that A. baumannii under iron restricted conditions express IROMPs along with production of catechol type siderophore in order to acquire iron from the external milieu.