It has been demonstrated that under iron-restricted conditions, Listeria monocytogenes can utilize iron-loaded transferrin (Tf) from a range of species as its sole source of iron for growth. Human transferrin conjugated to horseradish-peroxidase (HRP-Tf) bound directly to whole cells of L. monocytogenes. This binding was blocked by apotransferrin indicating that the receptor can bind transferrin in either the iron-bound or iron-free form. Transferrin-binding was not host specific because both bovine and equine transferrin inhibited the binding of HRP-conjugated human transferrin. SDS-PAGE and Western blotting of bacterial surface extracts revealed the presence of a transferrin-binding protein of approximately 126 kDa.

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Twenty-three strains of the seven recognized Listeria species were studied by using DNA-DNA optical hybridization. The level of error in the data was low. Our results supported the results of Rocourt et al. (J. Rocourt, F. Grimont, P. A. D. Grimont, and H. P. R. Seeliger, Cum. Microbiol. 7:383-388, 1982), although there was some overlap between Listeriu monocytogenes and Listeria innocuu. We suggest that there may be more than one cluster in the species L. monocytogenes or the species may form a large spectrum of relatedness. The level of intraspecies homology in L. monocytogenes is very broad, as determined in both this study and other studies. In their DNA studies, Rocourt et al. (10) divided what was the L. monocytogenes complex into the five species that are recognized today; this division was supported by a small number of biochemical differences (11). However, only six C1087T (= NCTC 11846T = ATCC 19119T = SLCC 2379T) C659 (= P L242) C663 (= P L72) C666 (= P L234) C667 (= P L102B) C214 (= SLCC 332/64) SLCC 7211 C1174T (= NCTC 10812T = ATCC 25401*)

It has been demonstrated that under iron-restricted conditions, Listeria monocytogenes can utilize iron-loaded transferrin (Tf) from a range of species as its sole source of iron for growth. Human transferrin conjugated to horseradish-peroxidase (HRP-Tf) bound directly to whole cells of L. monocytogenes. This binding was blocked by apotransferrin indicating that the receptor can bind transferrin in either the iron-bound or iron-free form. Transferrin-binding was not host specific because both bovine and equine transferrin inhibited the binding of HRP-conjugated human transferrin. SDS-PAGE and Western blotting of bacterial surface extracts revealed the presence of a transferrin-binding protein of approximately 126 kDa.

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