Host-Intestinal Microflora Interactions: Role of the Mucus and Gynolactose

Mucus and gynolactose might control host-Bjdobacterium interactions. Their respective roles were investigated in this study using gnotobiotic mice. By comparing glycoprotein SDS-PAGE profiles, mucus from various murine lines (NC, CF1, BALB/c and C3H) were differentiated. We attempted then to determine the intestinal substrates utilized by various bifidobacteria. First, NC and CF1 germfree mice received an inoculum of a murine species, B. animalis. Bacteria utilized the glycosyl fraction of several CF1. glycocompounds. No such extensive degradation was observed in NC mice. In constrast, both NC and CF1. mice responded to colonization by modifying hexosamine composition of their high molecular weight mucins. Three human species (B. bifidum, B. breve and B. longum) were then assayed for their in vivo capacity to degrade murine mucus from C3H mice. B. bifidum utilized extensively glycoproteins from the mucus, whereas B. longum and B. breve were unable to degrade them. However, none of the human strains led to intestinal mucins modification. Origin of the strains seemed to be a factor controlling the host response. Finally, gynolactose effect was investigated in germfree, B. breve-associated, and infant flora—associated C3H mice. Few modifications to mucus composition were noticed in the first two cases. In infant flora—associated mice, new intestinal glycoproteins and proteins were detected but bacterial counts were not changed. Host response to gynolactose might depend on the implantation of some unknown intestinal bacteria. It is likely that the proliferation of bifidobacteria shown in breast-fed infants does not correspond to a direct gynolactose promoting effect. But it is probably related to mucus modification induced by gynolactose.