Heme-iron and ecology of Escherichia coli within the porcine gut.

Growth of Escherichia coli was followed in sow whey by a turbidometric technique. Heme-iron clearly promoted bacterial growth, therefore free heme would be dangerous in small intestine by enhancing bacterial growth: duodenal brush border membrane (BBM) was seen to bind heme-iron, thus abolishing the growth promoting effect of this form of iron. Scatchard analysis of heme-binding onto BBM showed that heme became bound by a specific mechanism (KD approximately equal to 10(-7) M) as well as non-specifically. The absorption system for iron within the enterocytes should be considered an important antibacterial system within the gut.