Association of the diatom Thalassiosira pseudonana and E. coli captured by scanning electron microscopy. Image credit: Thomas Deerinck and Bogumil Karas.

Association of the diatom Thalassiosira pseudonana and E. coli captured by scanning electron microscopy. Image credit: Thomas Deerinck and Bogumil Karas.

Scientists from the J. Craig Venter Institute (JCVI), a not-for-profit genomic research organization in La Jolla, California, have published a paper outlining new synthetic biology methods to manipulate diatoms. The paper titled, “Designer diatom episomes delivered by conjugation,” was published April 21st in Nature Communications.

The researchers, led by first author Bogumil Karas, Ph.D. and senior author Philip Weyman, Ph.D., conclude that these new and efficient methods will enable better understanding of diatom genetics and facilitate advances in engineering these microoganisms to produce important products such as biofuels and chemicals.

JCVI researcher and senior author Philip Weyman, Ph.D.

JCVI researcher and senior author Philip Weyman, Ph.D.

While many researchers are working on ways to enhance diatoms and increase lipid production, there have not been efficient tools for large scale DNA delivery that can enable effective genetic engineering methodology in diatoms like those that exist for two main synthetic biology model organisms, Escherichia coli (E. coli) and Saccharomyces cerevisiae (yeast).

The JCVI-led team, some of whom are experts in diatom biology and others with expertise in synthetic biology, set out to discover and develop efficient genetic modification tools using episomes or plasmids. They were initially looking for diatom DNA sequences that allowed for plasmid replication but instead identified a yeast plasmid that replicates in diatoms and functions like an artificial chromosome.

JCVI researcher and first author Bogumil Karas, Ph.D.

JCVI researcher and first author Bogumil Karas, Ph.D.

The researchers then demonstrated that E. coli employs a mating process called conjugation that can be used to transfer the plasmid to the diatom. This is a very rapid and efficient genetic transfer process. The team then observed that E. coli can transfer plasmids into two genetically different diatom species, P. tricornutum and T. pseudonana, and that the plasmids replicate stably in both species.

In addition to the implications of their work in biotechnology applications, the team also concluded that the research likely sheds light into the evolution of diatoms and adds more evidence to the notion that conjugation is an important influence on microbial ecology in oceans.

“This technology is so easy to use and does not require any expensive reagents or equipment. It really lowers the barriers to genetic manipulation of algae so that any laboratory studying diatoms can do this,” said Dr. Weyman.

This research is supported by funds from Synthetic Genomics Inc., the United States Department of Energy and the Gordon and Betty Moore Foundation. Researchers from the Scripps Institution of Oceanography, University of California, San Diego, and the National Center for Microscopy and Imaging Research also contributed to the work in this paper.