Gut microbes have been engineered to have reduced urease activity in a bid to ameliorate hyperammonemia. In a proof-of-concept study, the existing gut microbiota was depleted in mice before inoculation with altered Schaedler flora (a defined set of eight bacteria with low levels of urease gene content and activity). Long-term reduction in faecal urease activity and ammonia production was observed upon colonization. Inoculation of the same microbial consortium in mouse models of acute and chronic liver injury resulted in decreased morbidity (cognitive impairment) and mortality.