Moving Shadows: the Voice of Bioluminescent Bacteria
by Ritwik Kaikini
The most fascinating light assumes its disguise in front of me as I open the petri dish. It looks blue and has its shades of yellowish-green. Victoria had streaked some bacteria on it a few days back.
We call the bacteria vibrio Fischeri. They live in the belly of the Hawaiian Bobtail Squid in the marine world.
A form of bacterial communication called Quorum Sensing occurs within these bacteria which deals with genes and chemistry in the most philosophical ways. Bonnie Bassler, the molecular biologist from Princeton University, explains this mechanism in a simple manner. When it’s a heavily moonlit night, the ocean floor no longer looks dark. It becomes visible like a canvas for organisms who swim in between the sunken sand and the surface of the water. Moving shadows form over the sand, owing to the movement of organisms above. The marine life living on the ocean floor can sense they are being hunted by tracing these shadows. What can we do to prevent these shadows?
A Hawaiian Bobtail Squid swims freely over this marine life. The bacteria inside its belly undergo a chemical reaction under the presence of oxygen to form purely organic light. Luciferin is oxidized under the presence of the catalyst, Luciferase, which results in light emission. This kills its own shadow. They can hover over any creature undetected and hunt them on the ocean floor. This comes at a price. The bacteria use a part of the Bob tail Squid’s nutrition to make this light. They depend on each other. One wants light. The other wants the food.
Anna Edwards and Victoria Nguyen, who are pursuing degrees in biology, worked with me to culture these bacteria and over the weeks of the fall 2016 semester, we developed brighter glowing bioluminescent bacteria.
Crossing generations of light results in brighter light. During observation, I kept the petri dish beside my bed and when I slept it felt like they were speaking to me in the nights using the medium of light.
I observed the bacteria overnight and they would start glowing in regions specific to different small colonies on the dish. These tiny regions never spoke concurrently. They gradually spoke out like all of us do when placed in a big crowd.
Jeremiah Gassensmith, an assistant professor of Biochemistry at University of Texas at Dallas, suggested the idea of ‘listening’ to these bacteria and using them as diagnostic devices in medicine. They can simultaneously light up different parts of the body if injected in the body and we can realize the bacteria’s death through the loss of light. This bioluminescent light is difficult to detect owing to its non- uniformity and faintness at times.
Hearing is considered one of the primary actions to detect abnormalities in different parts of the human body. Sonification of any of these parameters of the bioluminescence (be it brightness/contrast/area) can enable a new form of auscultation to listen to the death or life of these bacteria inside the body.
Our team, under the guidance of Jeremiah Gassensmith and Scot Gresham Lancaster, is working on a project called “Micro Lux Chants” where we want to sonify the life of bioluminescent bacteria. With help from one of my classmates, Adnan Naseem Khan, we have found a way to capture the bioluminescence on a suitable camera. We are currently working on using sonification software such as MAX/Msp to process these videos and try to listen to what the bacteria want to convey. A time lapse video is also under process.