Community Matters When Using Algae to Produce Energy

January 20, 2019

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(left) The diatom Phaeodactylum tricornutum and flagellated bacteria. (right) Researchers studied P. tricornutum enriched in carbon-13 (red) derived from fixation of labeled carbon dioxide and bacterial symbionts enriched in nitrogen-15 (green).
(left) The diatom Phaeodactylum tricornutum and flagellated bacteria. (right) Researchers studied P. tricornutum enriched in carbon-13 (red) derived from fixation of labeled carbon dioxide and bacterial symbionts enriched in nitrogen-15 (green).
Images courtesy of Xavier Mayali, Lawrence Livermore National Laboratory

The Science

Algae fix carbon. That is, they convert carbon dioxide in the air into other compounds, thus fixing atmospheric carbon in water or soil. Researchers showed that bacteria growing on certain algae increase carbon fixation. Further, the team found this increase in two species of microalgae via two different and species-dependent mechanisms.

The Impact

By fixing carbon, tiny algae can potentially produce renewable fuels reliably and affordably. But first they need to work better. ­­­­­This study shows that to improve algae's performance in producing energy, scientists need to consider the ubiquitous microbes, including bacteria, that intimately associate with algal cells on the microscopic scale.

Summary

The researchers observed mutualistic interactions between heterotrophic bacteria and two species of biofuels-relevant microalgae, Nannochloropsis salina and Phaeodactylum tricornutum, mediated by physical association between individual cells. At the bulk scale, microalgae in these co-cultures exhibited enhanced growth and yield. At the microscale, the researchers used the Lawrence Livermore National Laboratory nanoscale secondary ion mass spectrometry to observe that both species exhibited enhanced carbon fixation in response to the presence of the microbiomes, but there were divergent responses by each species to bacterial attachment. The research illustrates how P. tricornutum may be predisposed to interact mutualistically with bacteria via attachment, but N. salina does not share these traits. Attached bacteria benefit from these relationships by receiving more reduced carbon from their algal host compared to free living cells. Through the selection of bacteria that positively impact algal physiology, this work highlights one approach to ecologically engineer microbiomes conferring growth benefits to the algal host, potentially paving the way to cheaper, reliably produced, and renewable algae-based fuels and products.

Contact

Program Manager
Dawn Adin
DOE Office of Biological and Environmental Research, Biological Systems Science Division
Dawn.Adin@science.doe.gov

Xavier Mayali
Lawrence Livermore National Laboratory
mayali1@llnl.gov  

Rhona Stuart
Lawrence Livermore National Laboratory
stuart25@llnl.gov

Funding

The Department of Energy, Office of Science, Office of Biological and Environmental Research, Biological Systems Science Division, Genomic Sciences Program funded this research.

Publications

T.J. Samo, J.A. Kimbrel, D.J. Nilson, J. Pett-Ridge, P.K. Weber, and X. Mayali, "Attachment between heterotrophic bacteria and microalgae influences symbiotic microscale interactions." Environmental Microbiology (2018). [DOI: 10.1111/1462-2920.14357]

Related Links

Lawrence Livermore National Laboratory: Biofuels Scientific Focus Area