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Roles of the three Mycobacterium smegmatis katG genes for peroxide detoxification and isoniazid susceptibility
Author(s) -
Iwao Yasuhisa,
Nakata Noboru
Publication year - 2018
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/1348-0421.12574
Subject(s) - mycobacterium smegmatis , biology , peroxidase , gene , catalase , microbiology and biotechnology , hydrogen peroxide , strain (injury) , isoniazid , genetics , enzyme , biochemistry , mycobacterium tuberculosis , medicine , tuberculosis , pathology , anatomy
Three different katG sequences ( katGI, katGII and katGIII ) were identified in the Mycobacterium smegmatis genome. The contributions of the three katG genes to survival of the bacterium were examined by constructing disruptants of these three genes. The katGIII sequence did not produce a functional catalase‐peroxidase. Analyses of peroxidase activity and mRNA expression revealed that in wild type M. smegmatis , expression dominance between KatGI and KatGII was switched in the exponential and stationary growth phases. Susceptibility of the M. smegmatis gene disruptants to hydrogen peroxide (H 2 O 2 ) was tested in two growth phases. In the exponential phase, the katGI ‐null strain was more susceptible to H 2 O 2 than the katGII ‐null strain, indicating that KatGI plays a more important role in survival than KatGII in this growth phase. In contrast, in the stationary phase, growth of the katGII ‐null strain was inhibited at lower concentrations of H 2 O 2 . These results suggest that M. smegmatis has two types of catalase‐peroxidases, expressions of which are controlled under different gene regulatory systems. Isoniazid (INH) susceptibilities of the katG ‐null strains were also examined and it was found that katGI is a major determinant of M. smegmatis susceptibility to INH.