C57BL/6 and BALB/c mice: Microbiome composition and colonic cell population analysis.

Abstract

Purpose : To validate the richness, heterogeneity and composition of the gut microbiome and colonic monocytic populations in C57BL/6 and BALB/c mice locally housed.

Methods : Female (8-9 weeks) C57BL/6 and BALB/c mice were housed in separate cages, 3-5 mice/cage and acclimatized in our animal facility for one week. Then, caeca were removed, DNA isolated from their contents and 16S rRNA gene sequencing of the V4 region done. Differences in microbial α- and β-diversity were evaluated for each group. Flow cytometry analyzed populations of colonic macrophages and inflammatory monocytes between the two mouse strains before and after (n=3/group/time) corneal infection with 1×10⁶ CFU Pseudomonas aeruginosa (ATCC strain 19660).

Results : No differences in microbial richness were observed between the two mouse strains. However, bacterial heterogeneity and evenness were significantly reduced in the C57BL/6 vs BALB/c strain. The two groups also differed significantly in the composition and structure of their gut microbiomes. Data indicated increases in the relative abundance of Firmicutes and Verrucomicrobia specific to the BALB/c strain. In contrast, Bacteroidetes were increased in C57BL/6 mice. We also observed increased relative abundance in two species, B. thetaiotaomicron and L. johnsonii in C57BL/6 mice, agreeing with previous work by other research teams. Flow cytometry of colonic cells revealed no intrastrain differences in inflammatory monocytes between ocularly infected and uninfected mice. However, a significant increase in the number of colonic inflammatory monocytes was detected when comparing C57BL/6 with BALB/c infected mice.

Conclusions : We confirmed that two genetically different strains of mice show differences in the composition and structure of their gut microbiome. We provide evidence that ocularly infected C57BL/6 vs BALB/c mice have an increased number of inflammatory monocytes in the colon which may hold relevancy for their disparate response to corneal infection with Pseudomonas aeruginosa.

This is a 2021 ARVO Annual Meeting abstract.