Analysis Of The Diversity Of Lactic Acid Bacteria (LAB) In ICR Mouse Intestine And Preliminary Study Of The Relationship Between The LAB Composition With Diabetes

The gastro-intestinal (GI) tract of humans, rodents and numerous other mammalians harbour a complex microflora in which lactic acid bacteria (LAB) are considered to provide beneficial influences on the host. Recently, studies of probiotics have made it clear that the healthy effects of LAB are strain dependent and influenced by the indigenous bacteria, especially indigenous LAB of the host. So it is significant to study the composition of the indigenous LAB of mice and rats that are commonly used as models to study the relationship between probiotics and health. Meanwhile, we have found that some strains of Lactobacillus were related to the onset and development of diabetes when we studied the relationships between gut microbiota and STZ induced diabetes model through molecular ecological methods. It is of remarkable significance to isolate these strains and to verify the relationship between them and diabetes.Ninety-six LAB isolates were obtained with MRS medium (Difco) under anaerobic conditions from a 30mg fecal sample of a healthy male ICR mouse. Amplified Ribosomal DNA Restriction Analysis (ARDRA), Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR fingerprinting, and 16S rRNA gene sequencing classified all these isolates into 4 Lactobacillus species with L. reuteri (51 isolates) and L. johnsonii (30 isolates) being the dominant ones, each had 5 and 2 ERIC-PCR types respectively, with higher than 99.4% homology of their 16S rRNA genes within each species. The diversity of Lactobacillus spp. in the same fecal sample was confirmed with group-specific PCR-denaturing gradient gel electrophoresis (DGGE) and group-specific clone library analysis. This high strain-level diversity in a micro-niche may have significance for ecological adaptation of both indigenous Lactobacillus spp. and probiotic strains.Six strains (ERIC-PCR phylotypes) of Lactobacillus which potentially related to diabetes were screened by comparing the LAB group specific PCR-DGGE patterns of the 96 isolates and the clones of DGGE bands from the previous study. And the six strains were admininstered to ICR mice to verify their relationship with diabetes. Animal experiment revealed that the success rate of model establishment was decreased from 90% to 72% through oral administration of the mixture of the 6 Lactobacillus. Unfortunately, the mice in the prevention group were died in succession. Although we didn't figure out the reason of death of the animals in prevention group, we reconfirmed that these Lactobacilli were closely related to STZ induced diabetes model. Further studies are needed to find out the specific relationships and the mechanisms.