Characterization of Mycobacterium smegmatis mutants defective in 1-D-myo-inosityl-2-amino-2-deoxy-alpha-D-glucopyranoside and mycothiol biosynthesis

Mycothiol (MSH) is the major low molecular weight thiol in mycobacteria, Tw o chemical mutants with low MSH and one with no MSH (strain 49) were produc ed in Mycobacterium smegmatis mc(2)155 to assess the role of MSH in mycobac teria. Strain 49 was shown to not produce 1-D-myo-inosityl-2-amino-2-deoxy- alpha-D-glucopyranoside (GlcN-Ins), an intermediate in MSH biosynthesis. Re lative to the parent strain, mutant 49 formed colonies more slowly on solid media and was more sensitive to H2O2 and rifampin, but less sensitive to i soniazid. Complementation of mutant 49 with DNA from M. tuberculosis H37Rv partially restored production of GlcN-Ins and MSH, and resistance to H2O2, but largely restored colony growth rate and sensitivity to rifampin and iso niazid, The results indicate that MSH and GlcN-Ins are not essential for in vitro survival of mycobacteria but may play significant roles in determini ng the sensitivity of mycobacteria to environmental toxins. (C) 1999 Academ ic Press.