 genus *Clostridium* on the expression of IL-17A and IL-22 mRNA. The closely related genus "*Candidatus Arthromitus*" was also found to strongly promote IL-22 and IFN-γ, and was the only genus to strongly influence the cytokine response on day 21. These results are in agreement with previous reports of the stimulatory effects of "*Candidatus Arthromitus*" on the GI immune response[@b8][@b16][@b17][@b18][@b39][@b40]. Furthermore, we identified several other genera, such as *Phyllobacterium*, *Proteus*, *Comamonas*, *Lactococcus* and *Pandoraea* that likely influence GI cytokine mRNA levels in the terminal ileum. While these results need to be verified experimentally, they demonstrate the power of BMA to identify bacteria that may play important roles in shaping the GI immune response.

It was notable that neither *Clostridia* nor "*Candidatus Arthromitus*" were associated with *C. albicans* colonization. Conversely, other bacteria such as *Streptococcus* in the faecal pellets were strongly associated with *C. albicans* colonization but not with cytokine mRNA levels. These contrasting results suggest that in the faecal pellets, the bacterial influence on *C. albicans* colonization was either direct or mediated by other mechanisms that did not involve the host GI immune response. A possible exception is *Veillonella*, which was associated with both suppression of IL-21 and stimulation of *C. albicans* colonization in the terminal ileum. Our findings are supported by recent work by Vautier et al.[@b41] who showed that both IL-17 knockout mice and mice treated with an IL-1 blocker had normal levels of *C. albicans* GI colonization, which suggests that these cytokines may not play a significant role in controlling the level of colonization. Given these interesting and varied associations between the microbiota and host immune response, we expect that analysing an expanded panel of cytokines and immune effector cells could yield further insights into the host factors that govern *C. albicans* colonization.

Fungi other