Architecture and field operation of a portable digital holographic microscope for in situ measurements of bacterial motility

The development of a next-generation, portable digital holographic microscope enables the realtime volumetric characterization of bacterial behavior in extreme environments. This microscope is designed to observe bacteria in their native habitats, minimizing the experimental bias introduced by the extraction of samples for laboratory studies. The instrument, which operates at a wavelength of 405 nm and offers a spatial resolution of 1 micron, is fully self-contained with onboard computing and power, allowing hours of uninterrupted operation in the field. This digital holographic microscope is 180 mm x 300 mm x 135 mm and is less than 16 pounds, allowing easy transport to brine pools at the field sites described in this investigation. The instrument was field tested at the Boulby Underground Research Laboratory in the UK, where bacterial motility was observed and characterized in brine pockets undisturbed by human contamination. The holographic architecture of the microscope captures volumetric data at a video rate without moving parts, providing a stable long-term platform for field operation. This technology, identical to the proposed design for spaceflight instruments, will aid in the search for life on icy moons by improving our understanding of bacterial behavior in extreme conditions. Future developments of this platform will focus on refining data reduction algorithms and operational methodologies for Earth-based and space-based applications.