Cyanobacteria represent an underexploited source of bioactive natural products of interest to the pharmaceutical industry. Lack of development of these compounds as drug leads is due mainly to myriad practical problems with the producing strains including long doubling times, genetic intractability, and low compound yields. Previous attempts at heterologous expression in quick-growing, genetically amenable hosts such as Escherichia coli and Streptomyces spp. have encountered mixed success, especially with more complex natural products from non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) pathways. The most successful heterologous expression host to date is the filamentous freshwater cyanobacterium Anabaena sp. strain PCC 7120. Here, we examine the ability of heterologously expressed sigma factors identified in the genome of Anabaena sp. strain PCC 7120 to assist E. coli in the recognition of and transcription from native cyanobacterial promoters. A reporter gene expression assay examining the expression of chloramphenicol acetyltransferase from the promoter regions from complex cyanobacterial gene clusters was used to show that sigma factor All7608 is capable of recognizing multiple cyanobacterial promoters in E. coli. Attempts to produce lyngbyatoxin A from its native cyanobacterial gene cluster were unsuccessful, possibly hindered by deficiencies in recognition of cyanobacterial ribosomal binding sites by native E. coli translational machinery
