Gentamicin is a 4, 6-disubstituted aminocyclitol antibiotic complex synthesised by some members of the actinomycete genus
Micromonospora. In a search for the gentamicin biosynthetic gene cluster we identified, using a cosmid library approach, a region of the
M. echinospora ATCC15835 chromosome that encodes homologues of aminoglycoside biosynthesis genes including
gntB-a close homologue of the 2-deoxy-
scyllo-inosose synthase gene (
btrC) from butirosin-producing
Bacillus circulans. Insertional inactivation was achieved by homologous recombination with an internal
gntB fragment-containing suicide plasmid, delivered by conjugal transfer from
Escherichia coli. gntB disruptants were gentamicin non-producing mutants as assayed by an ELISA antibiotic detection system, proving the association of
gntB (or a downstream region) with gentamicin biosynthesis. The function of some open reading frames within the cluster, predicted by nucleotide database homology searching, is discussed with regards to their potential roles in gentamicin biosynthesis. The discovery of this genetic region represents the first report of a gene cluster involved in the biosynthesis of a 4, 6-disubstituted aminocyclitol antibiotic.
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