Characterization of a mycothiol ligase mutant of Rhodococcus jostii RHA1

Mycothiol (1D-myo-inosityl 2-[N-acetyl-L-Cysteinyl]amido-2-deoxy-alpha-D-glucopyranoside) is an important microbial thiol present only in actinomycetes. Rhodococcus jostii RHA1 degrades a wide range of xenobiotics, including polychlorinated biphenyls, nitriles, and N-nitrosodimethylamine. Analyses revealed that this strain produces two thiols, mycothiol and ergothioneine, found in the other actinomycetes. A mycothiol ligase mutant strain of R. jostii RHA1 deficient in the production of mycothiol was constructed. This mutant has a number of interesting characteristics: (a) it overproduces the intermediate glucosamine-inositol (1-O-(2-amino-1-deoxy-alpha-D-glucopyranosyl)-D-myo-inositol); (b) it is deficient in the biochemical degradation of a number of xenobiotics metabolized by the parent strain; (c) it shows increased susceptibility to a number of antibiotics; and (d) it shows unusual growth characteristics, exhibiting a long tag phase before normal exponential growth. The diverse phenotypes of the mutant indicate the utility of R. jostii RHA1 as a model for deciphering the various functions of mycothiol. (C) 2008 Elsevier Masson SAS. All rights reserved.