Do Bacteria Say Cheese When They Have Their Photo Taken?
Microbial photography. It’s a thing.
Right now, there’s a good chance that you have a sophisticated digital camera in your pocket, in the shape of a smartphone.
There’s also a high likelihood that it has a lens on both its front and back surfaces, enabling that extraordinary 21st-century technological breakthrough, the selfie.
We’re not sure how they worked it out, but it was estimated that as of December last year, there were 282 million selfies on Instagram.
It’s certainly come a long way since 1826 (or perhaps 1827) when the Frenchman Joseph Nicéphore Niépce took what is now the earliest surviving photograph made in a camera.
It wasn’t a selfie, of course, but the view from his window in the Burgundy region of France recorded on a piece of polished pewter coated with a type of bitumen, and apparently requiring an exposure of several days.
Not very practical for that duck face thing, then.
It took a while, but photography slowly – then rapidly – evolved, using a wide range of techniques that all basically boiled down to chemicals changing color in the presence of light.
However, maybe you’re thinking along the same lines as us: if chemicals can do this, what about bacteria?
In fact, a team led by biological engineering professor Chris Voigt – now at MIT – has been pioneering what you might call bacterial photography for the past 12 years.
Back in 2005, Professor Voigt and his team, then at UCSF, used genetically engineered bacteria to create black and white images.
The scientists began with that microbial workhorse E. coli, which is used in so many microbiological experiments.
E. coli doesn’t normally process light, so Professor Voigt’s team carefully transplanted two re-engineered genes from blue-green algae (which is a photo synthesizer) into the E. coli’s cell membrane.
One of these genes was able to code for a protein that reacts to red light.
In a procedure that’s perhaps analogous to an electrical relay, when this first gene was activated, the protein shut down the action of the second gene, a switch-off that turned an added indicator solution black.
Because bacteria are so very tiny, the good news was that this method enabled an insane resolution of 100 megapixels per square inch.
Although it seems churlish to label it so, the bad news was an exposure time that only marginally improved on Niépce’s several days.
You see, the earliest bacterial photograph required an image to be projected onto a dense layer of E. coli for four hours.
Now, we should stress at this point that the aim of this work wasn’t to create a new practical photography method, but rather to demonstrate the power of engineering bacterial cells so that their functions can be manipulated by exposing them to light.
Now Chris Voigt and his team have gone further.
Earlier this year they demonstrated the first color photographs made using bacteria.
They have engineered E. coli cells to respond exclusively to red, green or blue light, and when these genes are activated, they pass signals to yet more freshly created genes that have the ability to generate visible pigments the same color as the light they’ve absorbed.
These color images don’t have the same high resolution as their monochrome predecessors, but they do appear to be long-lasting.
A few years after being created, several of them are apparently still looking great hanging on the walls of the Voigt lab.
Making a color image with bacteria involves first re-engineering the cells using CRISPR gene editing tools.
Then, a petri dish containing agar – a jell-o-like growth medium – is loaded with a dense layer of E. coli.
Finally, the plate gets loaded into an incubator, which becomes a kind of camera.
A hole in the top of the incubator enables a bright color image to be projected down onto the plate.
And, a mere eight hours later, there you have it.
Pictures created by the lab have included a still life of fruit, a leaping Super Mario, and a reproduction of the famous lizard tessellation originally created by the Dutch graphic artist M.C. Escher in 1939.
Of course, bacterial cells such as E. coli cannot “see” in the literal sense, but Professor Voigt says genetic engineering has enabled them to exhibit at least some of what it takes to do so.
“It takes two components to see,” explains Voigt, “One is to sense the light, and the second is to interpret it in some way, so at a basic level you can respond, then compute something in response.”
See? Microbes can be smart, and bringing them and photography neatly together, we have just one question.
How did the E. coli bacterium take a selfie?
It used its cell.