Cyanobacterial alka(e)nes: strategies for improving their production via synthetic biology and studies on their requirement for optimal photosynthetic growth

To date, all sequenced cyanobacteria (>120 strains) have genes encoding an alka(e)ne or alkene synthase, consisting of either a polyketide sythase (Perez et al 2011) that converts fatty acids via an n+1 mechanism or a 2-enzyme system (fatty acyl redutase and aldehyde deformylating oxygenase, Schirmer et al 2010) that reduces acyl-ACPs to aldehydes, then deformylates the aldehydes to alka(e)nes. In many strains, the abundance of these compounds is quite high, being several-fold more numerous than chlorophyll. Although these compounds were first reported in cyanobacteria in the 1960’s, their biological function remains mysterious. We have found that in Synechocystis sp. PCC 6803, alkanes (heptadecane) are required for optimal growth. In addition, we have identified synthetic biology strategies to increase these compounds above their natural abundance.