Integrated analysis of transposon insertion sequencing and pangenome reveals core and lineage-specific essential genes in Mycobacterium avium subsp. hominissuis

Pulmonary disease caused by non-tuberculous mycobacteria (NTM-PD) is an emerging global health concern. Among NTM, Mycobacterium avium subsp. hominissuis (MAH) is the major causative agent of NTM-PD. Similar to Mycobacterium tuberculosis , MAH exhibits lineage-specific geographical distributions and host adaptations. Here, we characterized three MAH strains from the residential bathrooms of Mycobacterium avium complex pulmonary disease patients in Japan. A genetic population clustering analysis revealed that the three strains belong to the East Asia (EA) lineages that are predominant in Japan and Korea. Pan-genome analysis using the publicly available complete genome sequences of MAH and the newly sequenced MAH strains identified 3,313 core genes that are conserved among distinct MAH lineages. Identification of essential genes in the three strains was conducted using transposon insertion sequencing, and their gene essentiality profiles were compared to those of a previously studied sequence cluster 3 (SC3) lineage strain, MAC109. Despite their genetic diversity, nearly all essential genes were derived from the core gene set. In addition, we identified a set of common essential genes for the EA and SC3 lineages, as well as lineage-specific essential genes. Our results highlight the evolutionary and clinical importance of lineage-specific adaptations in MAH.