Xu et al. found that infected patients showed higher abundance of B. cellulosilyficus (Xu et al., 2022), whereas B. stercoris and P. copri were associated with ACE2 upregulation and increased proinflammatory cytokine production, respectively, in COVID-19 patients (Li et al., 2021; Lymberopoulos et al., 2022). This evidence concerns the gene ACE2 and COVID-19.