The iron uptake mechanisms of enteropathogenic Escherichia coli: the use of haem and haemoglobin during growth in an iron-limited environment

Abstract

Summary. The iron uptake mechanisms of enteropathogenic Escherichia coli (EPEC) were examined and compared with those of control E. coli strains. The incidence of aerobactin production was similar (39% and 37% respectively) in the two groups. The quantities of enterochelin produced by aerobactin-negative EPEC and control strains were similar, as were the quantities of enterochelin produced by aerobactin-positive EPEC and control strains. The ability to use haem or haemoglobin as an iron source in an iron-restricted environment was found in 80.4 % and 60.8 O h of EPEC strains respectively, and in 766 % and 56.6 % of control E. coli strains. The ability of E. coli strains to use these compounds was not related to the production of enterochelin or aerobactin or to the production of haemolysins, and may be an important characteristic of bowel organisms. When growing in an iron-limited environment, the iron contained in haemoglobin was used in preference to ovotransferrin-bound iron. During periods of haemoglobin-stimulated growth, the enterochelin uptake system was shown to be fully expressed and may be involved in transport of haemoglobin-derived iron into the cell. Uptake of ovotransferrin-bound iron took place immediately upon exhaustion of haemoglobin-derived iron. The ability to use iron derived from haem compounds represents an alternative iron uptake mechanism for organisms growing in an iron-limited environment and allows greater flexibility during growth in viuo.

The Yersinia high-pathogenicity island and iron-uptake systems in clinical isolates of Escherichia coli

“…Overall, the proportions of isolates that were capable of using haemoglobin and haemoglobin-haptoglobin were 80 and 63 %, respectively. Utilization of haemoglobin, transferrin and lactoferrin has also been reported previously (Law et al, 1992;Dall'Agnol & Martinez, 1999). E. coli was considered to be incapable of using the haemoglobin-haptoglobin complex (Eaton et al, 1982, Helms et al, 1984; however, the uropathogenic strain CFT073, which possesses multiple iron-uptake systems, can use this complex (Torres et al, 2001).…”

Ovotransferrin: Structure, bioactivities, and preparation

“…Furthermore, ovotransferrin in egg white is largely free of iron and therefore its role in the egg's antimicrobial defense system is very likely iron independent. Many microorganisms are able to acquire iron bound to transferrins, including ovotransferrin (Law, Wilkie, Freeman, & Gould, 1992). Bactericidal activities against Gram-positive Staphylococcus aureus and Bacillus cereus and the Gram-negative E. coli were reported in both holo-and apo-ovotransferrin (Ibrahim, 1997).…”

The Mammalian Neuroendocrine Hormone Norepinephrine Supplies Iron for Bacterial Growth in the Presence of Transferrin or Lactoferrin

“…Moreover, database searches of genome sequences have so far revealed no evidence for vertebrate-type adrenoreceptors among NE-responsive bacteria. The E. coli strain used in this work is wild type for enterobactin synthesis and utilization (15), but this alone is not sufficient to promote growth in serum-SAPI medium unless NE is also present. Mutants (entA and entF) deficient in enterobactin synthesis do not grow at all in serum-SAPI medium even in the presence of NE (unpublished data), suggesting that enterobactin is involved in some way in the NE responsiveness of E. coli, but whether the effect is direct or indirect is not yet known.…”