Modulation of rat cecal microbiota by administration of raffinose and encapsulated Bifidobacterium breve

Abstract

To investigate the effects of administration of raffinose and encapsulated Bifidobacterium breve JCM 1192T cells on the rat cecal microbiota, in a preclinical synbiotic study groups of male WKAH/Hkm Slc rats were fed for 3 weeks with four different test diets: basal diet (group BD), basal diet supplemented with raffinose (group RAF), basal diet supplemented with encapsulated B. breve (group CB), and basal diet supplemented with both raffinose and encapsulated B. breve (group RCB). The bacterial populations in cecal samples were determined by fluorescence in situ hybridization (FISH) and terminal restriction fragment length polymorphism (T-RFLP). B. breve cells were detected only in the RCB group and accounted for about 6.3% of the total cells as determined by FISH analysis. B. breve was also detected only in the RCB group by T-RFLP analysis. This was in contrast to the CB group, in which no B. breve signals were detected by either FISH or T-RFLP. Increases in the sizes of the populations of Bifidobacterium animalis, a Bifidobacterium indigenous to the rat, were observed in the RAF and RCB groups. Principal-component analysis of T-RFLP results revealed significant alterations in the bacterial populations of rats in the RAF and RCB groups; the population in the CB group was similar to that in the control group (group BD). To the best of our knowledge, these results provide the first clear picture of the changes in the rat cecal microbiota in response to synbiotic administration.

FIG. 1.

Alignment of probe sequences, their target sites, and the sequences of the corresponding sites in reference microorganisms of the large intestine (type strains). The probe names are in accordance with the Oligonucleotide Probe Database nomenclature (2). N indicates an A/T/C/G wobble nucleotide.

FIG. 2.

Epifluorescence images of bacterial cells from the four groups of rat cecal samples stained with DAPI (green) and hybridized with a B. breve species-specific oligonucleotide probe (PBR2) (red) in FISH analysis.

FIG. 3.

Partial electropherogram of HaeIII-, HhaI-, and MspI-derived T-RF profile for four rat cecal samples and two bifidobacteria. The size of each T-RF (in base pairs) is indicated along with the horizontal scale at the top of the GeneScan display.

FIG. 4.

PCA of T-RFLP profiles from four groups of rat cecal samples. The percent variation accounted for by each principal component is indicated along the corresponding axis, along with the principal-component loading values.