title: Diversity and distribution of microbial long-chain fatty acid biosynthetic genes in the marine environment.
abstract: Bacterial production of long-chain fatty acids via a polyketide synthase-related mechanism has thus far only been investigated in isolate-based studies. Here, the genetic capacity for production of long-chain fatty acids was investigated using a culture-independent approach. PCR primers targeting the keto-acyl synthase (KS) domain of the pfaA gene involved in omega-3 polyunsaturated fatty acid (PUFA) biosynthesis were used to construct clone libraries to investigate KS sequence diversity in disparate marine habitats. Of the 446 sequences recovered, 123 (27.6%) clustered with KS sequences involved in the synthesis of eicosapentaenoic acid (EPA, C20:5n-3), docosahexaenoic acid (DHA, C22:6n-3) and arachidonic acid (AA, C20:4n-6). The remaining 72.4% of clones formed environmental-only groups or grouped with the KS domains of pfaA homologues from organisms producing unidentified products. In total, 17 groups were recovered - four known and 13 newly identified. A query of metagenomic data sets revealed sequences related to EPA KS domains, as well as sequences related to four environmental-only groups discovered in the clone libraries. The phylogenetic affiliation and end product of these environmental-only KS clusters is unknown. These findings reveal a widespread capacity for long-chain fatty acid production in marine microorganisms, including biosynthetic pathways not yet characterized.
authors.affiliation: Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA.
authors.forename: Christine N
authors.initials: CN
authors.lastname: Shulse
authors.forename: Eric E
authors.initials: EE
authors.lastname: Allen
mesh_terms: D016718:Arachidonic Acid / Q000096:biosynthesis; D001419:Bacteria / Q000201:enzymology / Q000235:genetics*; D004281:Docosahexaenoic Acids / Q000096:biosynthesis; D015118:Eicosapentaenoic Acid / Q000096:biosynthesis; D004777:Environment; D064429:Fatty Acid Synthases / Q000235:genetics*; D015525:Fatty Acids, Omega-3 / Q000096:biosynthesis; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D014644:Genetic Variation; D054892:Metagenome; D010802:Phylogeny; D048630:Polyketide Synthases / Q000737:chemistry / Q000145:classification / Q000235:genetics*
chemical_list: D015525:Fatty Acids, Omega-3; D005231:Fatty Acids, Unsaturated; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid; D048630:Polyketide Synthases; D015118:Eicosapentaenoic Acid; D064429:Fatty Acid Synthases