Plant Synthetic Biology
As all fossil fuels are deemed to be exhausted in the future, a green economy is, in the medium term, without alternative. Algae’s ability to harvest solar energy and their low need for nutrients renders them easy to manage on a large scale. Already, the algal biotech industry ranges from biofuels to nutrition and even water remediation. This is a movement we wanted to get behind to contribute to a sustainable future.¹
Algae can be grown in a bioreactor for large protein yields.
Like most people, we are fascinated by algae. They produce most of the atmospheres oxygen and
their diversity and sheer masses exceed our imagination.³ Algae are the only things we want to have
floating around in our oceans. However, in the Mediterranean, there is already one particle of
micro-plastic for every two microorganisms. For us, this is unacceptable. We just had to support the
algae in defending their world against the synthetic intruders.⁴ In the coming millenium, together
with climate change and mass extinction, the plastic epidemic will probably be one of the issues to
trouble mankind the most. While in Germany the problem is less visible, in other countries the
global plastic pollution is providing distressing pictures. Far off the tourist hotspots, beaches
are buried under the wast masses of plastic bottles, bags, fishing supplies and many, many more. All
this is also our responsibility, as much of our plastic waste is outsourced to Asia. Still, the real
problem is not the plastic we can see everywhere, it is the plastic we don’t see. As plastic keeps
on accumulating, it is slowly breaking down into smaller and smaller particles, into micro- and
nanoplastic. These small plastic particles are being found everywhere:in the rivers and oceans, in
the arctic ice⁵, in the atmosphere⁶, in the soil⁷, in the human body⁸. Trough the food chain,
plastic reaches us en masse, and it carries loads of toxic additives and plasticizers. It is clear
that already now, but even more so in the future, recycling macroplastic will no longer be enough.
We have to focus microplastic as well.
Introducing Chlamydomonas reinhardtii
Chlamy can be grown photoautotrophically, or for quicker growth, on acatate as carbon source.
Our chassis, Chlamydomonas reinhardtii gives us the best of both worlds of
microorganisms
and plants. Its fast growth, its photoautotrophy and its ability to be grown mixotrophically, the
posttranslational modifications render it the perfect expression system. In the last months, we have
tweaked and nerded with Chlamy to make it a powerful secretion system as well, see the Kaiser
Collection below
Even before we decided to participate in the iGEM competition, it had been shown in some
studies at the Willmund lab that Chlamy will spontaneously attach to some forms of microplastic. A
good omen for our plan to functionalize the green alga to degrade PET. Also, in contrast to
bacteria, Chlamy does not produce a biofilm that would shield the plastic particles from the
enzymes. We quickly verified that the attachment also happens on PET and immediately knew we had to
harvests this power to increase the enzyme concentration at the PET surface.
A combination of electrostatic effects and flagellar entanglement leads to the adhesion of Chlamy to PET.
We manipulated Chlamy using the MoClo method (see below) so that it can break down
polyethylene terephthalate. It does so by secreting two enzymes capable of cutting PET polymers,
called PETase and MHETase.
We applied a newly discovered glycosylation signal, the sp20 tag, and showed that Chlamy does
not
have to hide behind strong secretors like B. subtilis or Streptomyces. We showed that algal cells
can be used for biorecycling and are confident that algal recycling is the way of the future. Chlamy
and its relatives are so versatile and easy to manipulate that one day, there wont be a job that
they can not do.
Advancing Chlamy
In 2018 our PI Prof. Schroda co-authored a paper on a newly developed modular cloning system for Chlamydomonas reinhardtii, a small, single cell green alga. With this so called MoClo system it is now super easy to manipulate Chlamy.² This work inspired us to choose Chlamy as our chassis and to encourage others to do the same. That’s why we, in collaboration with the iGEM team Sorbonne U Paris, created the Chlamy Guide “How to handle Chlamy” which will give future iGEM Teams as well as other professionals all the information, protocols, tips and tricks they need to work with Chlamy successfully. With this handy guide, which contained the collected knowledge of both our teams we hope to give Chlamy the push it needs to fulfill its true potential in algal biotech, in PET recycling and beyond. For this reason we also uploaded the “Kaiser Collection”, a list of basic and composite, codon optimized parts to be used in Chlamy, standardized and therefore applicable in every lab around the world. Each team looking to express/secrete proteins using Chlamy should use this collection, as we have fine tuned and optimized these sequences a lot. We want other teams to be able to start right away with their secretion, without first having to fathom the right secretion signal, antibiotic resistance or promoter. This way, we can focus on whats important, using the power of Chlamy for good. We firmly believe that further research on Chlamy will bear fruit and help make the planet cleaner, more sustainable and greener.
The future is green!
How to handle Chlamy
This guide contains all the information one needs to get started with Chlamy. Protocols, media, general information. It was a matter close to our hearts to return something to the community of synthetic biology. In the last months, we went from absolute beginners to somewhat knowing our way around with Chlamy. We wanted to pass on our collective knowledge, so we joined forces with the iGEM Team Sorbonne and created this guide:
References
- [1] www.labiotech.eu/features/algae-review-industry-biotech-greentech-biofuels-nutrition-scrubbing
- [2] Birth of a Photosynthetic Chassis: A MoClo Toolkit Enabling Synthetic Biology in the Microalga Chlamydomonas reinhardtii; Pierre Crozet, Michael Schroda; ACS Synthetic Biology 2018 7 (9), 2074-2086; DOI: 10.1021/acssynbio.8b00251
- [3] Witman, S. (2017), World’s biggest oxygen producers living in swirling ocean waters, Eos, 98, https://doi.org/10.1029/2017EO081067. Published on 13 September 2017.
- [4] deutschlandfunk.de, 2. Juli 2014, Jochen Steiner: Mikroplastik bedroht Lebewesen im Meer (7. Juli 2014)
- [5] Melanie Bergmann et al. White and wonderful? Microplastics prevail in snow from the Alps to the Arctic, Science Advances (2019). DOI: 10.1126/sciadv.aax1157
- [6] Atmospheric transport and deposition of microplastics in a remote mountain catchment; Steve Allen, Deonie Allen, Vernon R. Phoenix, Gaël Le Roux, Pilar Durántez Jiménez, Anaëlle Simonneau, Stéphane Binet & Didier Galop; Nature Geoscience volume 12, pages339–344 (2019)
- [7] Microplastic in soils: Analytical methods, pollution characteristics and ecological risks; Defu He, Lili Lei; TrAC Trends in Analytical Chemistry; Volume 109, December 2018, Pages 163-172
- [8] Presence of microplastics and nanoplastics in food, with particular focus on seafood; EFSA Panel on Contaminants in the Food Chain (CONTAM); https://doi.org/10.2903/j.efsa.2016.4501
