Quantification of Colwellia psychrerythraea motility in microgravity with a custom digital holographic microscope

An off-axis digital holographic microscope was constructed for flight on board the International Space Station (ISS), with manual insertion of samples by the crew and remote operation of the data acquisition software taking place from the ground. A series of 12 operations over a 6-week period allowed for direct observation of the growth and motility of the marine psychrophilic bacterium Colwellia psychrerythraea. The bacteria were grown at +2 ºC in cold stowage on board the ISS in 50 mL culture bags, and small volumes were transferred into imaging chambers by the crew during each operations session. Growth of cells from