Rebels with a cause: Engineering diatoms into fuel factories
Emily Trentacoste at NMFS Office of Aquaculture
Diatoms are rebels of the microalgae world. They have unique evolutionary histories, bafflingly diverse metabolisms and bizarrely intricate morphologies. Many of the characteristics that make diatoms such oddballs among microalgae also make them excellent candidates as sources for biofuels. Engineering microalgae to produce lipids for fuel is not a new concept; however, all engineering attempts thus far have resulted in organisms with decreased fitness, which thwarts the advantages of using microalgae to produce fuel in the first place. We characterized, identified and targeted a previously ignored pathway – that of lipid catabolism, or the breakdown of lipids – for engineering. By knocking down the function of a specific lipase using targeted antisense RNA techniques, we produced strains that accumulated four times as many fuel-relevant lipids as wild-type strains, but showed no decrease in growth or division. This work showed that contrary to popular thought, growth and lipid accumulation are not mutually exclusive in microalgae.
International Relations?: Exploring global diversity, dispersal, and environmental selection in a marine diatom species
Kerry Whittaker at NMFS Office of Protected Resources
Diatoms exhibit astounding levels of inter and intraspecific diversity, yet the mechanisms driving their diversification are little understood. I determined global population structure among > 450 isolates of the cosmopolitan, ecologically important diatom species Thalassiosira rotula. A“global snapshot” approach was used to sample isolates throughout a single year (2010) at sites distributed across the Atlantic, Pacific and Indian Ocean basins and hemispheres. Clonal diversity within sites was as high as 100%, and divergence between sites reached FST values upwards of 0.2. The presence of genetically distinct populations demonstrates that significant divergence can occur despite the high potential for dispersal in these planktonic organisms. Genetic distance was unrelated to geographic distance, instead, genetic connectivity over global geographic space and time was significantly correlated with abiotic (temperature) and ecological (chlorophyll a) factors of the marine environment. These data suggest that geographic distance is not a barrier to genetic connectivity among diatom populations; instead, vast genetic diversity and high genetic structure is maintained and supported by ecological selection occurring over space and time.