World's first success in comprehensive identification of essential genes for non-tuberculous mycobacteria prevalent in Japan - Potential to provide important basic information for target search for new antibacterial drugs -

A research group led by Assistant Professor Kotaro Sawai, Associate Professor Yusuke Minato, and Professor Yohei Doi of the Infectious Disease Research Center of Fujita Health University (Toyoake City, Aichi Prefecture), in collaboration with Professor Fumito Maruyama of the IDEC International Collaboration Organization of Hiroshima University (Higashihiroshima City, Hiroshima Prefecture), and Director Tomotada Iwamoto of the Kobe City Health Science Research Institute (Kobe City, Hyogo Prefecture), has conducted a joint research to identify non-tuberculous mycobacteria derived from patient living environments in Japan.*1Mycobacterium aviumsubsp.hominissuis(MAH), ``essential genes'' that are essential for survival.*2” were comprehensively identified.
Until now, research on MAH has often been conducted using strains with genetic strains that are different from those that are problematic in clinical practice in Japan, and the strains that are important in clinical practice have not been fully understood. In this research, we will be the first in the world to develop a transposon insertion sequence.*3Analysis and pangenome*4We integrated the analyzes and conducted a comparative analysis of the East Asian MAH strains prevalent in Japan and other strains.
As a result, we revealed the existence of essential genes that are common across genetic lineages and essential genes that differ between strains, and demonstrated for the first time the ``plasticity of essentiality'' in which gene requirements change depending on the strain.
These results are expected to advance the elucidation of the characteristics of MAH strains, which are a problem in clinical practice in Japan, and provide important basic information for the search for new antibacterial drug targets.
The results of this research were published in the online version of the British academic journal "Microbial Genomics" on June 26, 2026. *Paper information is listed at the end

• The world's first successful comprehensive identification of essential genes for MAH (East Asian lineage) prevalent in Japan
• Revealing low conservation of essential genes among MAH strains
• First elucidation of the existence of essential genes that differ in each lineage and the "plasticity of essentiality"

Pulmonary diseases caused by non-tuberculous mycobacteria (NTM-PD) have been increasing worldwide in recent years, and a particularly high incidence rate has been reported in Japan. MAH, the main causative bacterium, is widely present in soil and water environments and is divided into multiple genetic lineages. Among them, the strain that causes many cases in Japan and South Korea is called the "East Asia strain."
On the other hand, drug discovery research on NTM-PD has mainly been carried out in Europe and America, and the strains targeted for research have mainly been strains different from East Asian strains. As a result, the nature of the bacterial strains actually causing problems in Japan was not fully understood.
In particular, the extent to which there are commonalities and differences among strains regarding ``essential genes,'' which are essential for bacterial survival and are targets for antibacterial drugs, has remained an important issue.

In this study, we conducted gene essentiality analysis using transposon insertion sequencing (Tn-Seq) for MAH strains isolated from patient bathroom environments in Japan. Analysis requires the creation of a ``transposon mutant strain library'' in which mutations are randomly introduced into genes, but the efficiency of this creation is low in MAH, and so far only two strains in the world have been analyzed.
By optimizing conditions and improving protocols for multiple bacterial strains, the research group succeeded in creating a high-density library of three MAH strains derived from Japanese patient environments, and achieved comprehensive identification of essential genes.
Furthermore, as a result of comparative analysis of the data of the three East Asian strains obtained and existing data of other strains,
• Identified 124 core essential genes that are common regardless of strain
• More than 200 genes whose essentiality changes depending on the strain
It became clear that it would.
This demonstrated that the essentiality of genes is not fixed, but that there is "plasticity of essentiality" that changes depending on the strain and strain.

This study is an important achievement in that it clarifies for the first time the overall picture of gene essentiality in MAH, which is a clinical problem in Japan.
On the other hand, it became clear that there were fewer essential genes common between strains than expected, and there were large differences between strains. Although no major differences were observed in the target genes of existing antibacterial drugs, differences in the essentiality of some of the new drug target candidates were confirmed between bacterial strains.
In the future, it is expected that by further expanding the number of bacterial strains that can be analyzed and clarifying the characteristics of each strain in more detail, this will lead to the refinement of drug discovery targets and the construction of individualized treatment strategies.

*1 Non-tuberculous mycobacteria (NTM)
A general term for acid-fast bacteria that exist in the environment other than Mycobacterium tuberculosis and cause lung disease.
*2 Essential genes
Genes that are essential for the survival and proliferation of living organisms and are targets of antibiotics.
*3 Transposon insertion sequence (Tn-Seq)
A method of identifying genes necessary for survival by introducing random mutations into genes and analyzing their effects.
*4 Pangenome
The total number of genes possessed by all strains belonging to the same species. It consists of a "core gene" and variable genes that are common to all strains.

Paper title: Integrated analysis of transposon insertion sequencing and pangenome reveals core and lineage-specific essential genes inMycobacterium aviumsubsp.hominissuis
Authors: Kotaro Sawai, Marie Inokai, Motoko Shinohara, Yukiko Nishiuchi, Kanade Fujiyoshi, Yohei Doi, Tomotada Iwamoto, Kentaro Arikawa, Fumito Maruyama, Yusuke Minato
Affiliation: Fujita Health University, Hiroshima University, Kobe City Health Science Institute, etc.
DOI: 10.1099/mgen.0.001753