DISTRIBUTION OF THIOLS IN MICROORGANISMS - MYCOTHIOL IS A MAJOR THIOLIN MOST ACTINOMYCETES

Mycothiol deoxy-alpha-D-glucopyranosyl-(1-->1)-myo-inositol] (MSH) has recently been identified as a major thiol in a number of actinomycete s (S. Sakuda, Z.-Y. Zhou, and Y. Yamada, Biosci. Biotech. Biochem. 58: 1347-1348, 1994; H. S. C. Spies and D. J. Steenkamp, fur. J. Biochem. 224:203-213, 1994; and G. L. Newton, C. A. Bewley, T. J. Dwyer, R. Hor n, Y. Abaronowitz, G. Cohen, J. Davies, D. J. Faulkner, and R. C. Fahe y, fur. J. Biochem. 230:821-825, 1995). Since this novel thiol is more resistant than glutathione to heavy-metal ion-catalyzed oxidation, it seems likely to be the antioxidant thiol used by aerobic gram-positiv e bacteria that do not produce glutathione (GSH). In the present study we sought to define the spectrum of organisms that produce MSH. GSH w as absent in all actinomycetes and some of the other gram-positive bac teria studied. Surprisingly, the streptococci and enterococci containe d GSH, and some strains appeared to synthesize it rather than import i t from the growth medium. MSH was found at significant levels in most actinomycetes examined. Among the actinobacteria four Micrococcus spec ies produced MSH, but MSH was not found in representatives of the Arth robacter, Agromyces, or Actinomyces genera. Of the nocardioforms exami ned, Nocardia, Rhodococcus, and Mycobacteria spp. all produced MSH. In addition to the established production of MSH by streptomycetes, we f ound that Micromonospora, Actinomadura, and Nocardiopsis spp. also syn thesized MSH. Mycothiol production was not detected in Propionibacteri um acnes or in representative species of the Listeria, Staphylococcus, Streptococcus, Enterococcus, Bacillus, and Clostridium genera. Examin ation of representatives of the cyanobacteria, purple bacteria, and sp irochetes also gave negative results, as did tests of rat liver, bonit o, Candida albicans, Neurospora crassa, and spinach leaves. The result s, which indicate that MSH production is restricted to the actinomycet es, could have significant implications for the detection and treatmen t of infections with actinomycetes, especially those caused by mycobac teria.