Zbl. Bakt. 277, 340-344 (1992) © Gustav Fischer Verlag, StuttgartlNew York Sialic Acid as Receptor of Bacteroides fragilis Lectin-like Adhesin REGINA MARIA C. P. DOMINGUES, SiLVIA MARIA B. CAVALCANTI, ARNALDO F. B. ANDRADE, and MARIA CANDIDA S. FERREIRA Instituto de Microbiologia, Centro de Ciencias da Saude, Universidade Federal do Rio de Janeiro, Ilha do Fundao, 21944 Rio de Janeiro, RJ, Brasil Received December 6, 1991 . Revision received February 25, 1992 . Accepted March 12, 1992 Summary It was observed that sialic acid and macromolecules rich in this sugar were able to inhibit the hemagglutination activity (HA) of Bacteroides fragilis strains in low concentrations. Reversion of the HA and also of the adsorption to beads of Sepharose coupled to bovine submaxillar mucin, by this sugar residue corroborated the recognition capacity of the bacte- rial lectin-like adhesin. However, when erythrocytes were treated with clostridial neuraminidase, an increase in the HA of some strains was observed. Protease treatment of erythrocytes abolished the HA, indicating that cell receptors of B. fragilis are probably a glycoprotein maiety. Zusammenfassung Sialinsiiure und sialinsiiurereiche Makromolekiile hemmen in niedriger Konzentration die Hiimagglutinationsaktivitiit von Bacteroides fragilis. Hemmung der Hiimagglutination mit Kohlenhydraten sowie Absorptionsexperimente mit "bovine submaxillar mucin" -beschich- teten Sephadex-Siiulen bestiitigten die Vermutung, daB es sich urn lektiniihnliche Adhiisions- molekiile handelt. Inkubation der Erythrozyten in (Clostridium-)Neuraminidase bewirkte eine verstiirkte Hiimagglutination einiger Bacteroides-Stiimme; Proteasebehandlung hob die Hiimagglutination auf. Diese Effekte deuten darauf hin, daB die zelluliiren Rezeptoren fiir die Adhiision von B. fragilis offensichtlich durch Glykoproteinstrukturen reprasentiert wer- den. Introduction The mechanism of Bacteroides fragilis adherence to erythrocytes and epithelial cells has been the subject of many investigations in recent years (3,5,6,8,9,10, 14, 15). Nevertheless, the molecular basis of the interactions involved in this process and its