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Diversity and distribution of microbial long-chain fatty acid biosynthetic genes in the marine environment

Authors

  • Christine N. Shulse,

    1. Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
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  • Eric E. Allen

    Corresponding author
    1. Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
    2. Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA
      E-mail eallen@ucsd.edu; Tel. (+1) 858 534 2570; Fax (+1) 858 534 7313.
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E-mail eallen@ucsd.edu; Tel. (+1) 858 534 2570; Fax (+1) 858 534 7313.

Summary

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.

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