Gut microbiota composition is correlated to grid floor stress and behavior in the BALB/c mouse

Stress has a profound influence on the gastro-intestinal tract, the immune system and on the behavior of the animal. In this study, the correlation between gut microbiota composition determined by Denaturing Grade Gel Electrophoresis (DGGE) and tag-encoded 16S rRNA gene amplicon pyrosequencing (454/FLX) and behavior in 28 female BALB/c mice either exposed or unexposed (control group) to stress induced by grid floor housing was investigated. Plasma cytokine levels and plasma glucose levels were measured for each mouse. Stressing the mice clearly changed the GM composition and the genera Odoribacter, Alistipes and an unclassified genus from the Coriobacteriaceae family were found to increase significantly, while the genus Marvinbryantia was found to decrease significantly in the grid floor housed mice compared to the control group. The grid floor housed mice changed their amount of time spent in the Elevated Plus Maze and in the Light/Dark Box from baseline (i.e. before grid floor exposure) to end (i.e. after 2 weeks of grid floor exposure), as well as their Burrowing amount. As expected, the grid floor housed mice also had significantly longer immobility duration in the Tail Suspension Test, and in addition these mice increased their number of immobility episodes from baseline to end. Significant correlations were found between gut microbiota composition and IL-1a, IFN-?, closed arm entries of Elevated Plus Maze, total time in Elevated Plus Maze, time spent in Light/Dark Box, and time spent in the inner zone of the Open Field as well as total time spent in the Open Field. No significant difference was found for the evaluated cytokines, except an overall decrease in levels from baseline to end. A significant lower level of blood glucose was found in the grid floor housed mice compared to the controls, whereas the HbA1c level was significantly higher. It is concluded that grid floor housing is stressful and it changes the gut microbiota composition, which seems to influence certain anxiety-related parameters.