title: Aggregation of yeast cells: direct measurement of discrete lectin-carbohydrate interactions.
abstract: Aggregation of microbial cells mediated by specific interactions plays a pivotal role in the natural environment, in medicine and in biotechnological processes. Here we used atomic force microscopy (AFM) to measure individual lectin-carbohydrate interactions involved in the flocculation of yeast cells, an aggregation event of crucial importance in fermentation technology. AFM probes functionalized with oligoglucose carbohydrates were used to record force-distance curves on living yeast cells at a rate of 0.5 micro m s(-1). Flocculating cells showed adhesion forces of 121+/-53 pN, reflecting the specific interaction between individual cell-surface lectins and glucose residues. Similar adhesion forces, 117+/-41 pN, were measured using probes functionalized with the lectin concanavalin A and attributed to specific binding to cell-surface mannose residues. By contrast, specific interaction forces were not observed in non-flocculating conditions, i.e. in the presence of mannose or when using non-flocculating cells, pointing to their involvement in yeast flocculation. The single molecule force spectroscopy measurements presented here provide a means to study a variety of cellular interactions at the molecular level, such as the adhesion of bacteria to animal and plant tissues.
authors.affiliation: Unité de Chimie des Interfaces, Université Catholique de Louvain, Croix du Sud 2/18, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Touhami
authors.affiliation: Laboratorium für Organische Chemie, HCI H 317, ETH-Hönggerberg, CH-8093 Zürich, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Hoffmann
authors.affiliation: Laboratorium für Organische Chemie, HCI H 317, ETH-Hönggerberg, CH-8093 Zürich, Switzerland.
authors.forename: Andrea
authors.initials: A
authors.lastname: Vasella
authors.affiliation: Unité de Chimie des Interfaces, Université Catholique de Louvain, Croix du Sud 2/18, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Frédéric A
authors.initials: FA
authors.lastname: Denis
authors.affiliation: Unité de Chimie des Interfaces, Université Catholique de Louvain, Croix du Sud 2/18, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Yves F
authors.initials: YF
authors.lastname: Dufrêne
mesh_terms: D050260:Carbohydrate Metabolism; D005427:Flocculation; D037102:Lectins / Q000378:metabolism*; D008358:Mannose / Q000378:metabolism; D018625:Microscopy, Atomic Force; D012440:Saccharomyces / Q000166:cytology* / Q000378:metabolism
chemical_list: D037102:Lectins; D008358:Mannose