Community dynamics in the mouse gut microbiota: a possible role for IRF9-regulated genes in community homeostasis

Gut microbial communities of mammals are thought to show stable differences between individuals. This means that the properties imparted by the gut microbiota become a unique and constant characteristic of the host. Manipulation of the microbiota has been proposed as a useful tool in health care, but a greater understanding of mechanisms which lead to community stability is required. Here we have examined the impact of host immunoregulatory phenotype on community dynamics.

Denaturing gradient gel electrophoresis was used to analyse the faecal bacterial community of BALB/c and C57BL/6 mice and C57BL/6 mice deficient for either type I interferon (IFN) signalling (IRF9 KO mice) or type I and type II IFN signalling (STAT1 KO mice). Temporal variation was found in all mouse strains. A measure of the ability for a community structure characteristic of the host to be maintained over time, the individuality index, varied between mouse strains and available data from pigs and human models. IRF9 KO mice had significantly higher temporal variation, and lower individuality, than other mouse strains. Examination of the intestinal mucosa of the IRF9 KO mice revealed an increased presence of T-cells and neutrophils in the absence of inflammation.

The high temporal variation observed in the gut microbiota of inbred laboratory mice has implications for their use as experimental models for the human gut microbiota. The distinct IRF9 and STAT1 phenotypes suggest a role for IRF9 in immune regulation within the gut mucosa and that further study of interferon responsive genes is necessary to understand host-gut microbe relationships.