PIGLET ILEAL MUCUS CONTAINS PROTEIN AND GLYCOLIPID (GALACTOSYLCERAMIDE) RECEPTORS SPECIFIC FOR ESCHERICHIA-COLI K88 FIMBRIAE

The aim of this study was to characterize the Escherichia coli K88-spe cific receptors in mucus from the small intestines of 35-day-old pigle ts with the isogenic strains E. coli K-12(pMK005) (K88+) and E. coli K -12(pMK002) (K88-). These strains differed only in that the latter one cannot produce intact K88 fimbriae because of a deletion in the gene coding for the major fimbrial subunit. Adhesion was studied by incubat ing H-3-labeled bacteria with crude mucus, pronase-treated whole mucus , mucus fractionated by gel filtration, delipidated mucus, or extracte d lipids immobilized in microtiter wells. In addition, E. coli strains were tested for adhesion to glycolipids extracted from mucus by overl aying glycolipid chromatograms with I-125-labeled bacteria. The recent ly reported finding that K88 fimbriae bind to glycoproteins in mucus f rom the piglet small intestine was confirmed in two ways. Pronase trea tment of immobilized mucus reduced adhesion by 82%, and adhesion to de lipidated mucus was 14 times greater for the K88+ than for the K88- st rain. E. coli K88+ adhered to several of the fractions collected after gel filtration of crude mucus, including the void volume (M(r), >250, 000). Receptor activity specific for the K88 fimbriae was demonstrated in the lipids extracted from mucus, as the neutral lipids contained s ix times as much receptor activity as the acidic lipid fraction. Speci ficity was confirmed by demonstrating that adhesion to the total lipid s could be inhibited by pretreatment of the immobilized lipids with K8 8 fimbriae. Relative to K-12 (K88-), the K-12 (K88+) bacterial cells b ound more avidly to galactosylceramide when the neutral lipids were se parated on thin-layer chromatography plates. No adhesion to lipids in the acidic fraction separated on thin-layer plates was detected. Relat ive to adhesion of K-12 (K88-), adhesion of K-12 (K88+) to commerciall y available galactosylceramide immobilized in microtiter wells confirm ed the results with the thin-layer plates. It can be concluded that 35 -day-old piglet mucus contains both protein and glycolipid receptors s pecific for K88 fimbriae, the latter being galactosylceramide.