It has been established that the antimicrobial activity of lactoferrin towards Escherichia coli is enhanced by a direct contact between the protein and the microbial cell and that, in the case of E. coli K-12 strains, an antibacterial activity of lactoferrin unrelated to iron withdrawal is present. Evidence is now reported that lactoferrin binds to surface structures expressed in E. coli K-12 strains grown in either an ’excess’ or ’stress’ of iron. Under the experimental conditions used, lactoferrin binding both in the apo and in the iron-saturated form yields a maximum of 1.6 x 10⁵ bound molecules/E. coli K-12 cell; the amount of lactoferrin bound does not depend on the expression of the iron-regulated outer membrane proteins. In contrast, lactoferrin does not bind to E. coli clinical isolates. Apo-lactoferrin (at 500 μg/ml in a chemically defined medium) inhibits the growth of E. coli K-12 strains but not of clinical isolates. These findings suggest that the antibacterial activity of the protein could be associated to its binding to the cell surface.

Cited By (since 1996): 16Export Date: 26 August 2010Source: Scopus