| Abstract: | Indigenous bacteria in the alimentary tract are exposed to various bactericidalpeptides and digestive enzymes, but the viability status and morphological changes ofindigenous bacteria are unclear. Therefore, the present study aimed to ultrastructurallyclarify the degeneration and viability status of indigenous bacteria in the rat intestine.The majority of indigenous bacteria in the ileal mucous layer possessed intact cytoplasm,but the cytoplasm of a few bacteria contained vacuoles. The vacuoles were more frequentlyfound in bacteria of ileal chyme than in those of ileal mucous layer and were found in alarge majority of bacteria in both the mucous layer and chyme throughout the largeintestine. In the dividing bacteria of the mucous layer and chyme throughout theintestine, the ratio of area occupied by vacuoles was almost always less than 10%. Lysisor detachment of the cell wall in the indigenous bacteria was more frequently found in thelarge intestine than in the ileum, whereas bacterial remnants, such as cell walls, weredistributed almost evenly throughout the intestine. In an experimental control oflong-time-cultured Staphylococcus epidermidis on agar, similar vacuoleswere also found, but cell-wall degeneration was never observed. From these findings,indigenous bacteria in the mucous layer were ultrastructurally confirmed to be the sourceof indigenous bacteria in the chyme. Furthermore, the results suggested that indigenousbacteria were more severely degenerated toward the large intestine and were probablydegraded in the intestine. |
