Changes in GE2270 antibiotic production in Planobispora rosea through modulation of methylation metabolism

Thiazolylpeptide GE2270 is a potent antibiotic inhibiting protein synthesis in Gram-positive bacteria. It is produced as a complex of 10 related metabolites, differing mainly in the degree of methylation, by fermentation of the rare actinomycete Planobispora rosea ATCC 53773. Addition of vitamin B12 to the fermentation medium doubled total complex production and markedly changed the relative production of the various GE2270 metabolites, enhancing the biosynthesis of the more methylated component A. Among methylation inhibitors, the addition of sinefungin increased the amount of factor D2, which differs from component A in the lack of a methyl group. Since sinefungin is an S-adenosyl-L-methionine methyltransferase-specific inhibitor, these results indicate that the methylation step converting D2 into A involves an S-adenosyl-L-methionine methyltransferase. Simultaneous supplementation of vitamin B12 and sinefungin led to a twofold increase in D2 concentration, showing that vitamin B12, in addition to having an effect on the late methylation step, exerts a stimulating action on antibiotic backbone synthesis. This is possibly due to its role in an unusual pathway of serine synthesis peculiar to P. rosea metabolism. Finally, fermentation medium modifications were shown to be useful for the production of industrially valuable levels of components A or D2 in the GE2270 complex as starting points for the production of new interesting semi-synthetic antibiotics.