News

ELVIS is coming to Portland State
Author: Shaun McGillis, Research & Graduate Studies
Posted: December 11, 2018
EnterobacteriasIn a lab at Portland State University, physics professor Jay Nadeau and research assistant Iulia Hanczarek are huddled around computer monitors watching bacteria scuttle across the screens. Scuttle, but not swarm. The two are discussing the behavior of the bacteria, which to Hanczarek’s surprise are less enthusiastic than they typically are at meal time. It’s possible, Nadeau reasons, they’re not swarming because they’re getting too much food.
 

The bacteria’s blasé behavior isn’t the only thing different about the images on the monitors. As Nadeau points out, what we see on the screens is not a recording of an image as is typical in most types of microscopy. Instead, what we’re observing is a computer rendering of a three-dimensional hologram produced by a technique called digital holographic microscopy (DHM).

What’s unique about DHM is that it records light wave information as a digital hologram. Software, then, converts the image into a two-dimensional display on a screen, in this case, of bacteria swimming in a sample holder. One of the advantages of DHM, Nadeau explains, is that the hologram provides volumetric, or three-dimensional data, which means scientists can observe cell-sized objects moving about in space in real-time. It’s a feature that makes DHM particularly useful for studying tiny organisms and living cells in their natural environments. There are, however, limitations to DHM. For one, the process of rendering an image from a hologram is mathematically complex and sometimes results in poor image quality, making it difficult to identify what's on the screen.

Nadeau, along with Scott Fraser and Thai Truong of the University of Southern California (USC), has devised a way to overcome many of the limitations of DHM. They plan to combine DHM with Fluorescent Light Field Microscopy (FLFM). FLFM is another volumetric technique that takes snapshots of samples, recording fluorescence rather than light, which makes it particularly useful for imaging things like DNA, proteins, enzymes, or dyes.

Nadeau, Fraser, Truong, and PSU marine microbial ecologist, Anne Thompson recently received a three-year, $630,000 grant from the National Science Foundation to build not one, but two instruments that combine the functionality of DHM and FLFM microscopy. The team picked a familiar name for the unique microscope: ELVIS or the Extreme Life Volumetric Imaging System.

The instruments will be capable of instantaneously imaging larger sample volumes at a higher resolution than either a DHM or FLFM microscope could individually. The device will enable researchers to observe dynamic events, such as bacteria swimming or blood flowing in ways not possible with conventional microscopy. One of the instruments will serve as a benchtop unit and will be available for research purposes at USC’s Translational Imaging Center.

While the second ELVIS unit won’t be playing to packed houses, it will leave the building. The device Nadeau and her team are building at PSU is a submersible field unit. It will be housed in the Center for Life in Extreme Environments and available to researchers at Portland State and elsewhere in need of an instrument to conduct in situ observations in remote or extreme environments such as the open ocean, sea and glacier ice, and hydrothermal vents.

“With this microscope, researchers will be able to study microorganisms in the most hostile environments where they live,” Nadeau said. “A similar device could even be deployed on future missions to Mars to search for signs of microbial life there as well.”

In the long run, Nadeau thinks a tool such as ELVIS can have an impact on how biologists approach the study of microorganisms and cells in their natural environments, providing researchers an instrument capable of producing sharper images at a higher capacity than what can be achieved today.

Image: Enterobacteria; Credit: Bet Noire