, 1989; Pandey et al., 1994). Accordingly, both nonpathogenic as well as pathogenic bacteria (Ratledge & Dover, 2000) and fungi (Howard, 2004) require Fe for growth in the various environments in which they proliferate. Previous work has demonstrated the potential effectiveness of iron and other trace metal withdrawal for the inhibition of Saccharomyces cerevisiae growth (Feng et al., 1997a).

In this work, a trace iron methodology was developed and applied in order to study the Ponatinib cell line effect of iron removal on microbial growth in a chemically defined medium. In addition to using media with trace iron concentrations, microbial inhibition by the natural host defence Fe chelator, lactoferrin, clinically used chelators, such as desferrioxamine and deferiprone, and other strong chelators, such as bathophenanthroline sulphonate (BPS), EDTA and a novel carried chelator with hydroxypyridinone-like Fe-ligand functionality, DIBI, was also studied. The organisms chosen for this study were the well-known opportunistic pathogen Candida Alisertib supplier albicans (McCullough et al., 1996) and Candida vini (Barnett et al., 1983),

a related, but lesser-known nonpathogenic spoilage yeast. Candida albicans (ATCC 10231) and C. vini (ATCC 20217) were obtained from the Microbiology Laboratory Culture Collection at the Department of Food Science, University of Guelph, Canada. Desferrioxamine (Desferal) was donated by Ciba Geigy, now Novartis, Basel, Switzerland. Deferiprone, EDTA, BPS and bovine lactoferrin were obtained from ifoxetine Sigma-Aldrich. The developmental compounds DIBI and FEC-1 were donated by Chelation Partners. Apo-lactoferrin (i.e. Fe depleted) was prepared according to Holbein (1981). The other chelators were dissolved directly in the medium. The iron-binding capacity of the DIBI was determined

to be 800 μmol dry weight g−1 DIBI by adding varying amounts of Fe-citrate (1 : 3 molar ratio) to aqueous DIBI samples of known mass and then reading the Fe complex A530 nm, the main visible range absorption peak for the DIBI chelate as determined by an absorption scan. Throughout the work, the aerobic growth version of the chemically defined glucose-phosphate-proline (GPP) medium (pH 4.5) of Dumitru et al. (2004) was used with one modification: the mineral concentrate was prepared without the inclusion of FeSO4. Trace iron GPP was prepared by removing iron contaminations with the Fe-specific resin, FEC-1 (Feng et al., 1997b). For this, 5 g of hydrated and washed FEC-1 resin were batch contacted by shaking overnight with 1 L of complete GPP medium in a flask. After removal of the resin by filtration, the Fe-extracted medium was filter sterilized (0.22-μm nylon filter, Millipore) and stored in sterile plastic bottles at 4 °C. Typical trace iron concentrations attained using this method were 1.2 μg L−1. Different known iron concentrations were adjusted in the trace iron GPP by addition of appropriate amounts of a 0.