Vol. 150, No. 1, 1988 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS January 15, 1988 Pages 18-24 SIDEROPHORE PRODUCTION BY SALMONEZL4 TYPHI Asma Ismail Department of Medical Microbiology and Parasitology, School of Medical Sciences, University Sains Malaysia Received October 26, 1987 This study was initiated to determine the mechanismof iron-uptake in Salmonella typhi. Whenstressed for iron, microorganisms produce siderophores to obtain the necessary nutrient. Generally two types of siderophores exist: the phenolate-type predominantly produced by bacteria and the hydroxamate-type commonly secreted by fungi. Results of this investigation showed that 5. typhi produced siderophores of the phenolate- type since culture supernatant of the organism grown under iron-deprivation supported the growth of the phenolate-dependent auxotroph. The culture supernatant when extracted for phenolate siderophores, also supported the growth of the phenolate auxotroph but not the hydroxamate auxotroph. Production of phenolate-type siderophores were further confirmed using biochemical assays. These results showed that 2. typhi utilized the high- affinity iron transport system to obtain the necessary iron. Q1988 Academic Iron although abundant in the humanhost is made unavailable to micro- organisms since it is bound to host-iron binding proteins. The ability of microorganisms to acquire iron from the host is a prerequisite for patho- genecity (1, 2). Pathogenic microorganisms such as Salmonella typhi presumably must be able to utilize the iron sources available in the human host. An obligate parasite of humans, 2. typhi is the causative agent of typhoid or Enteric fever which remains as an important public health problem in underdeveloped countries. The organism is capable of invading the blood stream and disseminating into many organs of the body. Transferrin is probably the principal source of iron in the serum and lactoferrin is probably the main source of iron on mucosal surfaces (2). The mechanism by which 2. typhi obtains iron from these host-iron binding proteins has not been defined. Microorganisms have devised several mechanisms which can remove iron from host iron-binding proteins (3, 4). One such mechanismis a high- affinity iron acquisition system consisting of iron-chelating agents called siderophores and outer membrane proteins that serve as receptors for the iron-siderophore complexes and aid in their internalization. These iron- 0006-291X/88 $1.50 Copyright 0 I988 by Academic Press, Inc. All rights of reproduction in any form reserved. 18