Gravity Machine

InstrumentationBiophysics

Jan 24

Written By Prakash Lab

CATEGORY

Frugal Science Instrumentation

TAGS
microscopy tracking plankton

ABSTRACT

The ocean is the largest biosphere on our planet. Hidden right under the thin veil that forms the surface of the ocean, key micro-scale biological processes shape the past, present and future of the planet. The ocean absorbs a significant portion of carbon dioxide that we pump into the atmosphere. Many of these processes are regulated by microscopic life in the ocean – termed Plankton.

Every single day, marine plankton - microscopic in size - undertake vertical migrations from tens to hundreds of meters deep vertically. The behavior and microscale processes associated with freely suspended organisms, along with sinking particles underlie key ecological processes in the ocean. But what we know of light, temperature, nutrient distribution, and pressure, all change rapidly as we go deeper into the ocean. Mechanistically studying such multiscale processes in the laboratory presents a considerable challenge.

This work presents a completely new paradigm for tracking living cell motility - completely unhindered by any bounds. For the last 400 years, since the conception of microscopy, we have been confined in the release of X-Y plane for microscopy with a finite bounding box for microscopy. By developing a new paradigm of “hydrodynamic tread mill” for living cells - we have created a virtual reality arena for a motile cell that is unbounded in the z axis (aligned with gravity). Within a short period of 3 years - the invention of this tool has changed our view of life in the ocean. Currently we have collected the world’s largest motility database with roughly 300 unique species represented - including single cells as small as coccolithophore to large scale marine larvae and discovered a ubiquitous principle of gravity sensing across the ocean at micro-scale. These tools are further enabling us to directly measure the flux of carbon sequestration in open ocean - with latest expeditions to Antarctica and Arctic amongst a number of field expeditions we have conducted.

https://gravitymachine.org/
- Gravity Machine https://www.nature.com/articles/s41592-020-0924-7
- Active Sinking https://royalsocietypublishing.org/doi/full/10.1098/rsif.2022.0537
- Marine Snow https://arxiv.org/pdf/2310.01982.pdf
- Inflation induced motility https://www.biorxiv.org/content/10.1101/2022.08.19.504465v2

BIG QUESTION:

“How do you track single cells or microscopic particles only a few hundred microns in size, at microscale resolution, while allowing them to move freely along the axis of gravity, say a kilometer?”

Number of species imaged:

600+

Number of expeditions:

10+

Longest cellular migrations recorded:

200 meters

Number of units deployed:

10

What is Gravity Machine?

Inspired by the endless cycle of a hamster wheel, Gravity Machine is a ‘hydrodynamic treadmill’ with no bounds for motion along the axis of gravity that would allow for scale-free, vertical microscopy tracking of various organisms. This would allow scientists to observe and probe macroscale and ecologically relevant phenomena at microscale resolution. Beyond the marine context, Gravity Machine can provide biological measurements of cells and organisms in a suspended state by freeing them from the confines of the coverslip.

How it works

Gravity Machine is an upright circular chamber with an annulus of fluid serves as our 'endless' water-column. A horizontal light-microscope focused at either the 3 o'clock or 9 o'clock locations allows vertical movements of a cell or object to be tracked by compensatory rotation of the circular chamber such that a freely swimming cell is kept within the microscope's field-of-view. Linear tracking along the two horizontal directions allows full 3D localization of the cell. The imaging system acquires images at fast-rates and enables closed-loop 3D tracking using real-time computer vision algorithms as well as focus-tracking.