Department of Bacteriology, Graduate School of Medical and Dental Sciences, Niigata University, 1-757, Asahimachi-Dori, Chuo-ku, Niigata, 951-8510, Japan.
Department of Microbiology and Immunology, University of Minnesota Medical School, 689 23rd Avenue S.E. Microbiology Research Facility, Minneapolis, 55455, MN, USA.
Sci Rep. 2020 Mar 25;10(1):5449. doi: 10.1038/s41598-020-62287-2.
The global incidence of the human nontuberculous mycobacteria (NTM) disease is rapidly increasing. However, knowledge of gene essentiality under optimal growth conditions and conditions relevant to the natural ecology of NTM, such as hypoxia, is lacking. In this study, we utilized transposon sequencing to comprehensively identify genes essential for growth in Mycobacterium intracellulare. Of 5126 genes of M. intracellulare ATCC13950, 506 genes were identified as essential genes, of which 280 and 158 genes were shared with essential genes of M. tuberculosis and M. marinum, respectively. The shared genes included target genes of existing antituberculous drugs including SQ109, which targets the trehalose monomycolate transporter MmpL3. From 175 genes showing decreased fitness as conditionally essential under hypoxia, preferential carbohydrate metabolism including gluconeogenesis, glyoxylate cycle and succinate production was suggested under hypoxia. Virulence-associated genes including proteasome system and mycothiol redox system were also identified as conditionally essential under hypoxia, which was further supported by the higher effective suppression of bacterial growth under hypoxia compared to aerobic conditions in the presence of these inhibitors. This study has comprehensively identified functions essential for growth of M. intracellulare under conditions relevant to the host environment. These findings provide critical functional genomic information for drug discovery.
全球人类非结核分枝杆菌（NTM）疾病的发病率正在迅速上升。然而，对于最佳生长条件下以及与 NTM 自然生态相关的条件（如缺氧）下的基因必需性，我们知之甚少。在这项研究中，我们利用转座子测序技术全面鉴定了细胞内分枝杆菌生长所必需的基因。在细胞内分枝杆菌 ATCC13950 的 5126 个基因中，有 506 个被鉴定为必需基因，其中 280 个和 158 个基因分别与结核分枝杆菌和海分枝杆菌的必需基因共享。这些共享的基因包括现有的抗结核药物的靶标基因，如 SQ109，它靶向海藻糖单酰基转移酶 MmpL3。在 175 个在缺氧条件下作为条件必需基因显示出适应性降低的基因中，建议优先进行碳水化合物代谢，包括糖异生、乙醛酸循环和琥珀酸产生。在缺氧条件下，还鉴定到与毒力相关的基因，包括蛋白酶体系统和麦角硫因氧化还原系统，在存在这些抑制剂的情况下，缺氧条件下比有氧条件下更有效地抑制细菌生长，进一步支持了这一观点。本研究全面鉴定了与宿主环境相关的条件下细胞内分枝杆菌生长所必需的功能。这些发现为药物发现提供了关键的功能基因组信息。
