·Adhesion of Dairy Propionibacteria to Intestinal Mucus in the Absence-Presence of Dietary Cytotoxic Lectins

G. ZÁRATE, R. M.J. LORENZO-PISARELLO, A. PÉREZ-CHAIA.

Rosario, Argentina

Congreso; V Congreso Argentino de Microbiología General; 2008

Sociedad Argentina de Microbiología General

 Food and the metabolites generated during digestion and gastrointestinal transit play a major role in the consumer`s health. Many antinutritional and/or potentially toxic compounds are daily consumed by humans and animals. Among them, plant lectins are specific carbohydrate-binding proteins that are widespread in the diet, being present in many food items such as vegetables, fruits, cereals, beans and seeds. They are highly resistant to inactivation by cooking and by digestive processes and therefore it is likely that the colonic epithelium is exposed to many lectins that have retained their biological activity. In the intestinal lumen, lectins could act as antiproliferative agents or as tumour promoters by stimulating cell proliferation. They can also cause deleterious morphological and physiological changes in the intestinal mucosa such as inhibition of digestive enzymes, shedding of brush border membranes and shortening of microvilli that conduce to reduction of the absorptive function and nutrient utilization. In previous studies we have determined that some dairy propionibacteria have the ability to bind and remove some dietary lectins, preventing their cytotoxic effects on intestinal epithelial cells (IEC). However, adhesion to intestinal cells and mucus, a desirable property of probiotic bacteria, could be affected by their interaction with lectins. In fact, it has been observed that adhesion of propionibacteria to IEC was reduced but not abolished after binding lectins. In the present study, we determined the effect of jacalin (AIL), concanavalin A (ConA) and peanut lectin (PNA) on adhesion capability of dairy propionibacteria to intestinal mucus isolated from mucosa walls and luminal contents. Sterile multi-wells plates were coated with both fractions of mucus (0,5 mg mL-1) by an overnight incubation at 4°C and then propionibacteria (108 UFC mL-1) previously labelled with FITC were added and incubated under microaerophilic conditions for 60 minutes at 37 °C. Lectins (100 mg mL-1) and their complimentary sugars (0,5%) were added to mucus before or after bacteria. Adhered propionibacteria were quantified with an spectrofluorometer by measuring the fluorescence released after bacterial lysis with lysozyme. The same assay was performed quantifying the adhered microorganisms by staining bacteria with violet crystal. A decrease of bacterial adhesion to the mucus isolated from intestinal walls was observed when ConA, AIL and PNA got in contact with mucus before microorganisms whereas adhesion was not affected in the opposite condition. On the contrary, adhesion of propionibacteria to the luminal mucus was not affected by the presence of lectins suggesting a different mucus composition probably due to processing by microflora that use it as a source of nutrients in the intestinal lumen. Preincubation of propionibacteria with lectins also decreased their adhesion to mucus to different extents depending on the lectin assayed. Results suggest that consumption of foods containing these propionibacteria would be a tool to avoid lectins-mucosa interactions and its undesirable effects both in humans and animals.