Laser algae?

A recent paper got me thinking about a far-out solution to a major challenge to industrial-scale algae production

PROBLEM: shallow light
For algae production, one major barrier between bioenergy yields that can be reached in theory (or even in the lab) and the yields achieved in the field is the penetrance of light into a pond. In the lab, a dense culture of algae gets exposed to more light through the turbulence of a constantly swirling flask. In a pond, only the algae at the surface get exposed to light and produce energy.
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light-blocking effect of photosynthetic algae. NPQ is nonphotosynthetic quenching; P is photosynthetic energy. (Melis 2009)

Industrial yields could improve if more algae could get access to more light.

THE PRACTICAL SOLUTION: cut the chlorophyll

About two years ago, Anastasios Melis proposed a counterintuitive, yet elegant, solution to this problem. He proposed to reduce the chlorophyll content in each algal cell. You see, a lot of light ends up hitting chlorophyll overloaded with photons. If the amount of chlorophyll is reduced, light can go deeper into a culture and charge more algae, possibly improving overall yield.

light-blocking effect reduced with less chlorophyll. NPQ is nonphotosynthetic quenching; P is photosynthetic energy. (Melis 2009)

THE FAR-OUT SOLUTION: laser algae
A recent article appearing in Nature photonics just totally blew my mind. They turned human cells into lasers! The authors simply over-expressed green fluorescent protein (GFP) in cells, pumped up the GFP with pulses of light, and the cells fired off laser light as a result. The authors and others have proposed to use this technology to get light to previously inaccessable places in human tissue, and to potentially activate light-sensitive drugs.

However, why not use this technology to get light deeper into an algal culture?

A human cell emitting laser light in a dish. (Gather MC and Yun SH 2011)








THE FAR-OUT PROBLEM: too much equipment
In order to get cells to fire like a laser, you can't just overexpress GFP. You need a big apparatus to complette the laser. In the original paper, cells were plased in a resonator chamber and the GFP was activated with pulses of light to pump up the laser and cause it to fire. This is obviously a little too equipment intensive for game time.

However, there are ways to get single cells to produce light. Indeed single cells do this readily in nature!

The entire apparatus for creating a cell-based laser. Bottom, a microscope pulses light at a cell (blue arrows) The cell (placed between rectangular resonators) emits laser light (green arrows). d=20 micrometers. (Gather MC and Yun SH 2011)








BACK TO EARTH: the lesson here

While writing this post, I realize that the idea of cell-based lasers is way too ridiculously crazy to ever be used to produce algae based biofuel. However, I think another lesson can be drawn from this paper.

These authors used commonly available biological reagents to accomplish extraordinary tasks. For instance, basically any cell biology lab can create a GFP cell like the one described in this paper, and many do every day. Yet, the authors were able to take a common reagent that people have used for almost 20 years and do something extraordinary with it.

Perhaps, there is hope for some existing reagent to do something incredibly cool with algae. Could expressing the luciferase gene make algae glow like fireflies and get more light to more cells? Could a common mitogen enhance their growth? What other common reagents are available that could boost the yield of industrial algal biofuels?

REFERENCES
Gather MC and Yun SH. "Single Cell Biological Lasers". Nature Photonics. volume 5 (2011): 406-410.

Melis A. "Solar energy conversion efficiencies to photosynthesis: Minimizing the chlorophyll antennae to maximize efficiency". Plant Science. volume 177 (2009): 272-280.