MMP9 and infection: Indeed, infection with ΔespO, which attenuates (yet not abolish) nutritional immunity, is associated with specific dysbiosis, particularly affecting the abundance of Firmicutes. Similarly, infection of mice lacking Mmp9, which is found in reduced abundance in ΔespO, with WT C. rodentium also resulted in increased abundance of Firmicutes, as well as Lactobacilli [53].