Intestinal Glycolipids and Their Possible Role in Microbial Colonization of Mice

The alimentary tract is colonized by more than one hundred species of and more than one thousand billion microbes (per gram contents) . It is well known that the microbes colonized characteristically according to the site of the alimentary tract and species and physiological conditions of the host animal such as age (16, 17, 19) . Comparative studies between germfree and conventional animals clearly show that the intestinal microbes greatly affect physiology and morphology of the intestine of the host animal. However, we have not yet been able to obtain precise mechanisms of the difference between germfree and conventional animals in spite of great efforts thus far. On the other hand, the sphingoglycolipids are now studied from the aspect of the host receptor-intestinal microbe interaction. The glycolipids are very abundant in the microvillus membrane of the small intestinal epithelial cells (11, 14) . The composition of these glycolipids are different among species (3), developmental ages of the animals (12, 18), and between normal and pathological conditions of the host animals (6, 9) . And also these glycolipids have, at least in vitro, high affinity for the microbes (10) as well as the enterotoxins produced by pathogenic microorganisms (27) . Thus there is some reason to consider that the glycolipid might be a mediator between host animals and intestinal microbes. In this review, we summarize what changes occur in the intestinal glycolipids by association of the intestinal microbes with germfree animals, discuss the mechanism of this glycolipid change, and finally consider what roles these glycolipids play in the colonization of the intestinal microbes.