Biosynthesis of 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate in bacteria

Corynebacterium ammoniagenes mutants capable of accumulating 2-C-methyl-D-e rythritol-2,4-cyclopyrophosphate (MEC) in the absence of an exogenous oxida tive stress inducer were obtained. At the logarithmic growth phase, these m utants displayed decreased superoxide dismutase (SOD) activity and synthesi zed lower amounts of isoprenoids (carotenoids and naphthoquinones) than wil d-type cells. Screening the microorganisms for the capacity for MEC accumul ation revealed such bacteria among the gram-negative, facultative animal an d plant parasites Xanthomonas campestris, X, maltophilia, and Pseudomonas p utida. Iodoacetate did not inhibit MEC biosynthesis in corynebacteria, and no preferential incorporation of radiolabeled C-1 or C-6 atoms of glucose i nto the MEC molecule was observed, which was in agreement with the recently suggested scheme of a mevalonate-independent pathway of isoprenoid biosynt hesis, in which MEC is believed to be an intermediate.