The active lung microbiota landscape of COVID-19 patients

With the outbreak of COVID-19 causing by SARS-CoV-2, the interaction between the host and SARS-CoV-2 was widely studied. However, it is unclear whether and how SARS-CoV-2 infection affects lung microflora, which contributes to COVID-19 complications. Here, we analyzed the metatranscriptomic data of bronchoalveolar lavage fluid (BALF) of 19 COVID-19 patients and 23 healthy controls from 6 independent projects and detailed the active microbiota landscape in both healthy individuals and COVID-19 patients. The infection of SARS-CoV-2 could deeply change the lung microbiota, evidenced by the α-diversity, β-diversity and species composition analysis based on bacterial microbiota and virome. Pathogens (such as Klebsiella oxytoca causing pneumonia as well), immunomodulatory probiotics (such as Lactic Acid Bacteria and Faecalibacterium prausnitzii , a butyrate producer) and Tobacco mosaic virus (TMV) were enriched in the COVID-19 group, suggesting a severe microbiota dysbiosis. The significant correlation between Rothia mucilaginosa , TMV and SARS-CoV-2 revealed drastic inflammatory battles between the host, SARS-CoV-2 and other microbes in the lungs. Notably, TMV only existed in the COVID-19 group, while Human respirovirus 3 only existed in the healthy group. Our study provides insight into the active microbiota in the lungs of COVID-19 patients and will contribute to the understanding of the infection mechanism of SARS-CoV-2 and the treatment of the disease and complications.