Engineering the precursor pool to modulate the production of pamamycins in the heterologous host S. albus J1074.

Pamamycins, a group of polyketides originally discovered in Streptomyces alboniger, induce sporulation in Streptomyces and inhibit the growth of Gram-positive bacteria, Mycobacterium tuberculosis and fungi. The pamamycin biosynthetic gene cluster encodes 6 ketosynthases that utilize a variety of three-carbon to five-carbon CoA thioesters as starter and extender units. This promiscuity in production results in an up to 18 different derivatives during fermentation.

Generation of new compounds through unbalanced transcription of landomycin A cluster.

The biosynthetically well-studied landomycin A cluster has been used to demonstrate the unbalancing of gene transcription as an efficient method for the generation of new compounds. Landomycin A structural genes were decoupled from the native regulators LanI and LanK and placed under the control of a single synthetic promoter and expressed in a heterologous host Streptomyces albus J1074. In contrast to their native quantitative and temporal regulation, these genes were transcribed as a single polycistronic mRNA leading to the production of four novel and two known compounds.

An influence of the copy number of biosynthetic gene clusters on the production level of antibiotics in a heterologous host.

Streptomyces albus J1074 is a well-known host for heterologous expression of secondary metabolites. To further increase its potential and to study the influence of cluster multiplication, additional φC31-attachment site was integrated into its genome using a system for transposon mutagenesis. Four secondary metabolite clusters were expressed in strains with different numbers of attachment sites, ranging from one to three copies of the site.

Insights into the pamamycin biosynthesis.

Pamamycins are macrodiolides of polyketide origin with antibacterial activities. Their biosynthesis has been proposed to utilize succinate as a building block. However, the mechanism of succinate incorporation into a polyketide was unclear.

Elaiomycins K and L, new azoxy antibiotics from Streptomyces sp. Tü 6399*.

Elaiomycins K and L, two new azoxy-type antibiotics, were detected by HPLC-diode array screening in the culture filtrate extract of Streptomyces sp. Tü 6399. The structures were determined by high-resolution MS and 2-dimensional (1)H and (13)C correlated NMR spectroscopy including (15)N-NMR experiments and established these compounds as new members of the elaiomycin family.