ACE2 and COVID-19: On the other hand, ACE2 downregulation can have positive consequences: Zuo et al. (138) observed that several Bacteroides species (Bacteroides dorei, Bacteroides thetaiotaomicron, Bacteroides massiliensis, and Bacteroides ovatus) are already known to be able to downregulate ACE2 expression in mice, inversely correlated with SARS-CoV-2 content in the feces of COVID-19 patients, suggesting a protective role of Bacteroides against SARS-CoV-2.