Distribution and stress resistance of resident lactobacilli in mouse intestinal tract

In this paper, we studied the spatial distribution and stress responses of resident Lactobacillus in various intestinal regions in order to clarify the ecological and functional properties of the microbes in mouse normal microflora. Lactobacillus reuteri and Lactobacillus intestinalis were identified as resident species by 16S rDNA analysis. Both lactobacilli were present in all regions of the intestinal tract (duodenum, jejunum+ileum, cecum and colon) at almost the same ratios based on colony shapes on LBS agar and the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) profiles using a genus-specific primer pair. Survivability of L. reuteri against heat shock, acid and bile salt treatments was markedly higher than that of L. intestinalis. Furthermore, almost all isolates of L. reuteri obtained from all intestinal regions grew in MRS broth with 0.5% bile salts, while almost all of the isolates of L. intestinalis failed to grow in the broth with 0.1% bile salts. These results suggest that resident lactobacilli, L. reuteri and L. intestinalis, in mice are able to colonize all intestinal regions with different environmental conditions, regardless of their stress response potentials.