Glycine origin of the methyl substituent on C7'-N of octodiose for the biosynthesis of apramycin.

Apramycin is unique in the aminoglycoside family due to its octodiose moiety. However, either the biosynthesis process or the precursors involved are largely unknown. Addition of glycine, as well as serine or threonine, to the Streptomyces tenebrabrius UD2 fermentation medium substantially increases the production of apramycin with little effect on the growth of mycelia, indicating that glycine and/or serine might be involved in the biosynthesis of apramycin. The 13C-NMR analysis of [2-13C] glycine-fed (25% enrichment) apramycin showed that glycine specifically and efficiently incorporated into the only N-CH3 substituent of apramycin on the C7' of the octodiose moiety. We noticed that the in vivo concentration of S-adenosyl methionine increased in parallel with the addition of glycine, while the addition of methione in the fermentation medium significantly decreased the productivity of apramycin. Therefore, the methyl donor function of glycine is proposed to be involved in the methionine cycle but methionine itself was proposed to inhibit the methylation and methyl transfer processes a previously reported for the case of rapamycin. The 15N NMR spectra of [2-13C,15N]serine labeled apramycin indicated that serine may also act as a limiting precursor contributing to the -NH2 substituents of apramycin.

Rothia amarae sp. nov., from sludge of a foul water sewer.

A Gram-positive bacterium, strain J18(T), isolated from sludge of a foul water sewer, was subjected to a polyphasic taxonomic study. Phylogenetic analysis of the bacterium based on its 16S rDNA sequence showed that it belongs to the genus Rothia and forms a distinct phyletic clade with the type strain of Rothia nasimurium. Morphological, physiological and chemotaxonomic characteristics supported the assignment of this organism to the genus Rothia and distinguished it from the type strains of all validly described Rothia species. Therefore, it is proposed that this bacterium be classified in the genus Rothia as Rothia amarae sp. nov. The type strain is strain J18(T) (= AS 4.1721(T) = JCM 11375(T)).