Bugs In Space: Sending a Microscope to the ISS and the Search for Life Elsewhere

Abstract: We have recently described a design for a vibration-stable digital holographic microscope (DHM) coupled to a light field microscope (LFM) that permits simultaneous intensity (brightfield), fluorescence, and quantitative phase imaging (QPI) through a thick (1 mm) sample volume. This design is ideal for quantifying aspects of microbial behavior such as 3D motility and biofilm formation. The “zig-zag” or “reverse and flick” motility exhibited by marine organisms, such as those of the genus Vibrio, has been much less studied than the “run and tumble” swimming of soil and gut bacteria such as Escherichia coli. Vibrio swim differently near surfaces than in open solution, and can adhere and form biofilms. These studies are important for understanding infections that humans might acquire during spaceflight; the genus Vibrio includes important pathogens, such as V. cholerae, the causative agent of cholera. Motility plays a large role in Vibrio pathogenicity and any alterations in microgravity might have important implications for astronaut health. These studies can only be performed in extended microgravity, since changes to the bacteria occur over a time course of days to weeks, and simulated microgravity experiments on Earth have yielded results that often conflict with real microgravity findings.

We have recently been accepted for a flight on the International Space Station (ISS) for 2024 to look at Vibrio motility using our instrument. A good deal of work goes into preparing the microscope for flight, from compliance with NASA safety regulations to developing chambers for storage of live Vibrio. I will show some of our work as we prepare to fly, and discuss how these flight preparations help set the stage for later applications. Our eventual goal is to use microscopy as part of a suite of instruments to look for microbial life on “Water Worlds,” such as Europa or Enceladus. Another goal is to use the results of the Vibrio studies to help guide health and safety recommendations for astronauts. Finally, I will discuss future goals and projects looking for life in a wide variety of extreme environments, including nearby sites such as the glacier caves on Mt. Hood and Mt. St. Helens.