Epithelium-associated bacteria in the gastrointestinal tract of Arctic charr (Salvelinus alpinus L.). An electron microscopical study

Aims: The primary aim tvas to use transmission electron microscopy (TEM) an d scanning electron microscopy (SEM) to define the location of epithelium-a ssociated bacteria in the digestive tract: of the salmonid fish, Arctic cha rr (Salvelinus alpinus). Methods and Results: TEM and SEN examination of the gastrointestinal tract demonstrated substantial numbers of ovoid and rod-shaped bacterial cells as sociated with the microvillous brush borders of enterocytes. Bacteria were found at the tips of microvilli as well as between adjacent microvilli. End ocytosis of bacteria by epithelial cells was observed in two regions (pylor ic caeca and midgut). Conclusions: Electron microscope examination of the gut is an important too l for evaluating the microbial ecology of the fish digestive tract ecosyste m. Significance and Impact of the Study: The results of the current study clea rly demonstrate that the intestine is involved in bacterial endocytosis.