Adherence and ingestion of Escherichia coli serotype 055 by trophozoites of Entamoeba histolytica

Carbohydrate-binding activity present on the Entamoeba histolytica cell surfaces was found to mediate the adherence of two types of bacteria, Escherichia coli serotype 055 and Salmonella greenside 050. Adherence was inhibited by low-molecular-weight carbohydrates (10 mg/ml) such as galactose, lactose, and N-acetylgalactosamine, as well as by asialofetuin and the lipopolysaccharide extracted from E. coli 055. Mild periodate oxidation of the bacteria inhibited their adherence, whereas heat inactivation, glutaraldehyde fixation, or gamma-irradiation had no effect. On the other hand, pretreatment of trophozoites with glutaraldehyde, cytochalasin B, or cold (5 degrees C) abolished adherence. None of these treatments, however, affected the attachment of bacteria that contain on their cell surface type I pili with mannose-binding capacity. These findings lend further support to our earlier observations on how amoebae interact with bacteria.