Fatty acid composition of lipids in the maternal diet and establishment of a Lactobacillus sp. strain in the digestive tract of suckling gnotobiotic mice and rats.

Adult gnotobiotic mice and rats, monoassociated with a homofermentative strain of Lactobacillus sp. of intestinal origin, were fed either a commercial rodent chow A or a semisynthetic diet B. Similar numbers of lactobacilli were established in their gastrointestinal tract whatever diet they ate. The lactobacilli were established in the digestive tract of the newborn of A mothers at 2 days but were hardly established in mouse or rat pups of A mothers than in their mouse homologues. Comparative analysis of milk lipids in the A and B series showed a linoleic acid (18:2 n-6) content which was three times higher in the B than in the A series. Two diets S and H differing only by their lipid fractions, which, respectively, presented the same fatty acid compositions as lipids from diets A and B were then given to two others lots of Lactobacillus monoassociated mice. The establishment kinetics of the strain were the same in the mouse pups of these two lots precedently observed in the B series. The difference observed in the establishment kinetics of the Lactobacillus strain in the digestive tract of suckling gnotobiotic mice was thus attributed to other dietary factors than the fatty acid composition of the maternal diet.

["Lactobacillus murinus" n. sp., a new species of the autochtoneous dominant flora of the digestive tract of rat and mouse (author's transl)]. / Lactobacillus murinus N. Sp., une nouvelle espèce de la flore dominante autochtone du tube digestif du rat et de la souris.

Lactobacillus murinus, a new species isolated from rat and mouse digestive tracts, is described. It belongs to the subgenus Thermobacterium although it is able to ferment pentoses. The electrophoretic mobilities of soluble proteins and lactic dehydrogenase, the guanine + cytosine content (43.7%), the L-lysine-D-Aspartic acid cell wall (b type, Kandler), the immunological relationship with other Lactobacillus species and also the aminoacid requirements show that it has to be assigned to a new species, Lactobacillus murinus. This species settles in the digestive tract of rodents in their first days of life and remains ther as a dominant flora throughtout the whole life of the animal.