S110: Characterization of the Biofuel Hydrocarbons of Marine Cyanobacteria: Targets for Genetic Manipulation

All cyanobacteria possess the capacity to produce hydrocarbons from fatty acids yet not all accomplish this through the same metabolic pathway.  One pathway involves a two-step conversion of fatty acids first to fatty aldehydes and then alkanes which involves a fatty acyl ACP reductase (FAAR) and aldehyde deformylating oxygenase (ADO).  The second pathway involves a polyketide synthase (PKS) pathway that first elongates the acyl chain followed by decarboxylation to produce a terminal alkene (olefin) (OLS).  This investigation characterized the hydrocarbon composition and biosynthetic pathways of a wide variety of cyanobacteria, many of which had never been characterized before and represent under-investigated groups of cyanobacteria.  This expanded perspective on hydrocarbon composition and biosynthetic pathways revealed new double bond (2- and 3-heptadecene) and methyl group positions (3-, 4- and 5-methylheptadecane) for a variety of strains as well as evolutionarily informative patterns of pathway distribution.  Sixty-one additional strains possessing the FAAR/ADO pathway and ten additional strains possessing the OLS pathway were identified and found to form cohesive phylogenetic clades with one exception which may have acquired the OLS pathway via horizontal gene transfer.  Characterization of the structural diversity and phylogenetic distribution of these pathways reveals novel traits that can be potentially exploited for biofuel applications.